Superstition and the Supernatural

The Torah contains many commandments against various forms of witchcraft and superstition. Nevertheless, there seem to be several examples of superstition approved of by Chazal. In order to attempt to resolve the apparent contradictions, we need to try to clarify how we are supposed to relate to witchcraft, and what exactly the Torah is forbidding.

Necromancy

The first description that we have of use of a forbidden means of divining is when Shaul HaMelech asks the ov-woman to wake Shmuel HaNavi from the dead. We are told that Shaul knew that it was Shmuel, and that Shmuel admonished Shaul for awakening him. He then repeated a previous message that the kingdom has been taken from him, and added that tomorrow he (Shaul) would be with him (Shmuel, i.e. dead[1]).[2]

The language that Shaul knew that it was Shmuel seems to imply that it really was. The apparent corollary is that the prohibition of consulting an ov was made despite the fact that it really works. However, the Radak quotes a dispute between the Geonim about how to understand what happened, and all are in agreement that the actions of the ov are 'nonsense, empty, false and futility.' Some say that it was all a trick performed by the woman (and the word 'knew' is not meant literally). Others explain that in this case Hashem decided to resurrect Shmuel, shocking the ov-woman.

This position is corroborated by the Rambam, who writes: "All of these things (forms of divining) are false and dishonest, and they are the means that the early idolaters used to mislead the nations into following them. It is not fitting for Yisrael, who are the most wise, to be drawn after these nonsenses or to consider that they have any purpose. … Anyone who believes in these things or similar, and thinks that they are truth and a matter of wisdom, just that the Torah forbids them, is nothing but one of the fools and those lacking in understanding …"[3]

The Ramban disagrees, claiming that the results of divining have 'already been publicised in front of viewers.' He explains that when Hashem made the world He implanted in it a nature which would lead to various events, but He also gave the stars and other forces the power to change it. The Torah forbids Jews from using these forces to change the natural order, put in place by Hashem.[4]

The Vilna Gaon goes further, criticising the Rambam sharply. He writes: "Philosophy lead him (the Rambam) astray with most of its teachings, to explain the gemara all metaphorically and to detach it from its simple meaning. I do not, chas v'shalom, believe them, not part of them nor their multitudes. Rather, all the words (of Chazal) are according to their simple meaning, although they have depth. Not the depth of the philosophers, which must be thrown into the waste as it is really superficial. Rather, (the depth) of the possessors of truth."[5]

The Gaon is referring here to many cases where Chazal do seem to describe real powers of witchcraft. His strong belief in literal interpretations of Agada is extreme (see Drush and Divrei Agada), but in this case I am inclined to agree with his understanding of Chazal in the places that he quotes. However, this does not necessarily mean that this is the only view in Chazal.[6] And even if it was, this does not forbid us from thinking differently (see Divine Providence, Free Will and Coincidence).

Halachic Implications

The issue that is perhaps more bothersome for rationalists like myself is the seeming occurrence of halachos based on a real understanding of witchcraft. The clearest example of this is the distinction made between a 'magician' who 'does an action' and one who merely creates an illusion. One who does an action is punishable by death, whereas one who creates an illusion is exempt from (human) punishment.[7] If 'magic' has no real power, what is 'doing an action'?

In reality, this should not trouble us any more than the agaddic sources in Chazal that mention the power of witchcraft. Although the words of Chazal are absolutely binding for halachic purposes, this has very little relevance here. If someone 'did an action' of sorcery he would be liable to the death penalty, but any beis din has the right to decide that no action was done.[8]

Demons

We also find halachic sections of gemara that relate to the occurrence of demons. A mishna tells us that one who hears a voice coming from a pit giving instructions to write a get for his wife, may act upon these instructions as the agent of the one trapped in the pit.

The gemara questions why we are not concerned about the possibility that the voice might be that of a demon, deliberately misleading us. The gemara concludes that the rule of the mishna only applies if the one hearing the voice can also see a 'reflection of a reflection' of the person in the pit. Demons do not have a 'reflection of a reflection,' thus we can be sure that the one giving the instructions is a human being.[9]

The Rambam seems to ignore this explanation of the gemara. He states that one who hears a voice coming from a pit may carry out the instructions to write the get, without stipulating the need to see a 'reflection of a reflection.'[10] Various suggestions have been made as to how this fits into the gemara,[11] but to anyone familiar with the writings of the Rambam it is clear that a concern for demons was not something that he would be willing to consider as legitimate. There simply are too many laws related to mysticism that he omits from Yad HaChazaka.

What right did the Rambam have to do this? No-one can argue with halachic rulings of the gemara! Presumably, the answer is that when a halachic ruling is based on a certain perception of physical reality, we do have the right to reject this perception based on improved scientific knowledge (based on an assumption that Chazal would also have ruled differently with the benefit of the same knowledge). Only when it comes to understanding of the Torah, the authority of Chazal is absolute.[12]

Simanim

When it comes to defining what is forbidden as witchcraft, the rulings of the gemara are definitely binding. The gemara tells us that "regarding a house, a child and a woman, although there is no sorcery, there is a siman."[13] Rashi explains that the case is a person who built a house, had a baby or got married and subsequently succeeded or failed in a business venture (three times according to the conclusion of the gemara). It is forbidden to rely on this as a guarantee that this trend will continue, but there is a good chance that it will.

The Rambam explains differently. In all of these cases it is still forbidden to act differently based on the siman (even without relying on it a hundred percent). The only thing that is permitted is to comment after the fact that building a house, getting married etc. was a good siman.[14]

With this in mind, we can try to understand the idea behind simanim practice more widely. Elsewhere, the gemara says that since simanim are a genuine concept, a person should be used to seeing (some texts read: eating) a gourd, fenugreek, leek, beet and a date on Rosh Hashana.[15] The various commentaries explain that these things symbolise the things we want for the year ahead.

What exactly is the gemara saying we can achieve by seeing (or eating) these fruits? According to Rashi, perhaps these simanim may have some effect on the year ahead (although one mustn't rely on this). However, these simanim seem much more far-fetched than building a house, getting married or having a baby.

According to the Rambam, the only way I can see to resolve this gemara halachically is by explaining that the purpose of the simanim is not to directly affect the year ahead. They are to remind us that all the things we want in the year ahead are being decided on Rosh Hashana, and to act accordingly.

In reality, the Rambam does not mention these simanim at all in Yad HaChazaka (or anywhere else). It could well be that he felt that it contradicts the gemara about the house, the child and the woman. If it is forbidden to act differently based on simanim, it certainly is forbidden to orchestrate simanim in order to attempt to influence the future.

Miracles

Our distance from superstition is not because we are afraid of believing in anything supernatural. At least in my view, the various miracles performed by Hashem described by the Torah are to be taken reasonably literally, and not explained as naturally occurring phenomena.[16] I am aware that different opinions exist,[17] but I believe that there is not sufficient justification to stray from the simple meaning of the pesukim.

The severity that the Torah attaches to witchcraft and superstition is because we are supposed to direct our service to Hashem, and not to other imaginary forces (or even to real forces according to those who believe in them). The Rema quotes a dispute about making a siman for something in the future, and concludes (based on Tehilim 32:10): "The one who acts wholesomely and trusts in Hashem will be surrounded by kindness."[18]

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[1] See also Brachos 12b, where Chazal explain that this is an allusion that his death would atone for his sins and bring him to Olam Haba.

[2] Shmuel 1, 28:7-19.

[3] Hilchos Avoda Zara 11:16

[4] Commentary on the Torah, Devarim 18:9-12. There seems to be an explanation there as to why Hashem gave such power to 'change His plans,' but at least for the moment I do not understand it.

[5] Bi'ur HaGra, Yoreh Deah 179:13

[6] See for example Avoda Zara 55a.

[7] Sanhedrin 67a

[8] Practically, this question would only come up after the Sanhedrin is restored, as until then beis din does not have the power to judge capital cases. And the Sanhedrin will have the right to reject even halachic rulings of Chazal, making the whole problem redundant.

[9] Gitin 66a

[10] Geirushin 2:13

[11] See for example Kesef Mishne ibid.

[12] In other words, Chazal's understanding of a Torah law is binding, but their understanding of science is not. For example, Chazal define for us what is considered melacha and thus forbidden on Shabbos. They decided that killing any creature that reproduces sexually is considered melacha, and we cannot argue with this definition. They also decided that lice do not reproduce sexually and thus may be killed on Shabbos (Shabbos 107b), but as this has been proved inaccurate by science this leniency should not be relied on (this topic is more complicated, see for example this article at length).

[13] Chulin 95b

[14] Avoda Zara 11:5. He also explains the case of the child differently, asking a child which passuk he is learning and inferring a good omen from it.

[15] Horayos 12a

[16] See Moreh Nevuchim 2:25, where the Rambam explains that the main proof that the world was created (and is not eternal) is from the supernatural wonders in the Torah.

[17] See for example Bechor Shor, Shemos 9:8

[18] Yoreh Deah 179:4

The Mikveh and its Significance

After re-organising the labels on this blog, I realised that until now I have not yet written anything in the Taharos (ritual purity) category. As I am also currently going over the laws of Mikvaos (ritual baths), this post is the natural addition.

Background

Nowadays ritual purity and the use of the mikveh is a relatively small part of religious life. True, women need to dip once a month for about a quarter of their lives (from marriage till menopause, minus most of pregnancy and breastfeeding). Those of us who visit Har HaBayis (see Building the Beis Hamikdash) also immerse ourselves prior to each visit. We all use the keilim mikveh when we buy new food utensils. Some have the custom to go to the mikveh at other times, not required by halacha. But all of this pales into insignificance compared to what was and will be necessary when we have a Beis Hamikdash.

In those times, all are required to purify themselves three times a year, when coming to Yerushalayim to celebrate Yom Tov.[1] Kohanim need to be pure almost constantly (even when not serving in the Beis Hamikdash), in order to eat t'ruma. Even non- kohanim need to purify themselves extremely frequently, whenever coming into contact with t'ruma and challa (separated from dough).

This was no simple task. Illustrating just one example, the Mishna discusses how one immerses a bed in a mikveh in order to purify it.[2] This is not an example of Chazal discussing rare cases, but a regular occurrence in those days. In the future, each building (if not each apartment) will almost certainly need to have its own mikveh. In partial preparation, it makes sense for us to understand a little bit about what this entails.

Mayim She'uvim

The hardest obstacles to overcome when constructing a mikveh are the interrelated issues of mayim she'uvim (literally 'drawn water') and tevila b'keilim (immersion in vessels). The basic idea is that the water must gather naturally, not transported in utensils. The source and nature of these halachos are subject to fundamental disputes, which we must explain.

Chazal infer that mikveh must be similar to the alternative mentioned in the same passuk, a spring. As springs are created 'by the act of Heaven,' a mikveh must also be.[3] Thus a mikveh must consist of water not gathered in vessels, usually rain water that collects. However, in a seeming contradiction, the gemara tells us that this requirement is a rabbinic one.[4]

Rashi and others therefore explain that a mikveh consisting entirely of mayim she'uvim, or a majority of mayim she'uvim, is invalid on a Biblical level. The gemara deals explicitly with a case where the majority of the mikveh was made up of rain water. In this case, adding three lugin (about a litre) of mayim she'uvim before the mikveh has the required 40 se'ah (about 320 litres/0.32 m³) of rain water, invalidates the mikveh on a rabbinic level.

The Rambam and others disagree. They say that although the law of she'uvin is derived from a pasuk, this is only an asmachta (literally support, the term refers to an allusion or code found by the rabbis which is not the main meaning of the pasuk). Thus according to Biblical law, even mayim she'uvim are kosher for a mikveh.

According to this view, the obvious question is why did the rabbis feel it necessary to forbid the use of mayim she'uvim? Tosfos explain that even according to Torah law, immersion in water held in a vessel (and not in the ground) is invalid. The rabbis disqualified all water that had been in a vessel, to prevent the possibility of someone making a mistake and thinking that any gathering of water can be used.[5]

The Rambam does not agree with this. Firstly, he writes that according to Torah law one could achieve ritual purity by immersion in any gathering of water (including in a vessel).[6] Furthermore, it is clear from his words that the problem with immersion in a vessel stems from the issue of she'uvin, not the other way round.[7] According to this, we need to explain the reasoning behind the law of she'uvin differently.

Even according to Tosfos, we need to try to understand why the Torah invalidated immersion inside a vessel. Likewise, according to those who maintain that a mikveh consisting entirely of mayim she'uvin is invalid according to Torah law, we need to attempt to find the reasoning behind this.

Ritual and Spiritual Purification

More generally, we need to ask why the Torah obligated a person to immerse in a mikveh at all. The answer to this is indicated clearly by Chazal in many places, who compare ritual purification to spiritual purification. To quote one famous example from the Mishna:

אמר רבי עקיבא: אשריכם ישראל! לפני מי אתם מיטהרין מי מטהר אתכם? אביכם שבשמים, שנאמר (יחזקאל ל"ו) "וזרקתי עליכם מים טהורים וטהרתם." ואומר (ירמיה י"ז) "מקוה ישראל ה'" מה מקוה מטהר את הטמאים אף הקדוש ברוך הוא מטהר את ישראל.

יומא פרק ח, משנה ט

Says R' Akiva: Happy are you Israel! In front of who are you purified and who purifies you? Your Father in Heaven, as it says "I will throw upon you pure water and you will be purified (Yechezkel 36). It also says "Hashem is the Mikveh of Israel"- just like a mikveh purifies the ritually unclean, so too HaKadosh Baruch Hu purifies Israel!"

Yoma 8:9

The Chinuch explains that the idea of purity through water is based on the fact that the world was all water at the beginning of Creation. Thus one who immerses himself entirely in water can imagine that he is being 'created' again, and renew his ways. The rabbis invalidated water in vessels, or water that had been in vessels, as one who immerses in this water cannot imagine that the whole world is water.[8]

Solutions

As it is not practical to expect people to go to a spring, lake or sea every time they need to purify themselves, and a mikveh consisting entirely of rain water will quickly become unsanitary, creative solutions are necessary.

In my mind, the number of solutions available for the problem of mayim she'uvim is one of the strongest indications that the invalidity is entirely rabbinic. If the real source for the requirement of 'creation by Heaven' is the comparison to spring water, it would have been necessary to find additional sources for all the leniencies.[9] If, on the other hand, the rabbis made this requirement for the reason given by the Chinuch, we have a simple explanation. Whenever there was enough of a connection to naturally occurring water, Chazal felt that the objective can still be achieved.

There are two main solutions, known as zeriya ('sowing' mayim she'uvim in kosher mikveh water) and hashaka (having mayim she'uvim come into contact with a body of kosher mikveh water). Zeriya is a concept that applies when there already is the required forty se'ah of rain water in the mikveh. Any water added subsequently does not invalidate the mikveh, even if the original forty se'ah is now a tiny percentage.

Making use of this, the water in modern mikvaos can be changed regularly. The original forty se'ah of rain water gathers in one pit, and the immersion takes place in a much bigger pit next to it. Regular tap water is released into the first pit (called the bor zeriya), and allowed to overflow (through a pipe designed for this) into the second one (the bor tevila).

However, some believe that there is a halachic problem with this method. The gemara says that although one can add a se'ah to the mikveh and then remove a se'ah from it, this is only until the majority of the mikveh (i.e. if one removes the majority of the original mikveh water by this method, it is invalidated).[10] Many rishonim say that the gemara cannot be talking about the addition of mayim she'uvim, as it is clear from many sources that mayim she'uvim never invalidates a full mikveh. Therefore, they are forced to explain that this gemara deals with the addition of fruit juice (or liquids other than water).[11]

Others write that addition of a majority of mayim she'uvim and removal of an equivalent amount does invalidate the mikveh. Although addition of any amount of mayim she'uvim does not disqualify a mikveh, if one subsequently removes water it does.[12] Seemingly, as the water in the bor zeriya is replaced regularly, it becomes invalidated according to this view.

The truth is that even among the rishonim who are stringent about removing water from the mikveh directly, there is a dispute in the case of the bor zeriya.[13] The Beis Yosef suggests a reason for this distinction, based on the explanation of the Ramban. When the water is removed directly it looks as if the kosher water is being replaced with mayim she'uvim. If we allowed this, people would think that even a mikveh consisting entirely of mayim she'uvim is kosher. When the water just spills out indirectly, this concern does not exist.[14]

Nevertheless, almost all modern mikvaos do not rely on a bor zeriya alone. They also have a bor hashaka, another pit of rain water connected to the bor tevila through a small opening. Mayim she'uvim in the bor tevila becomes kosher mikveh water when it touches the water in the bor hashaka. Due to various concerns about supervision, common practice is not to rely on hashaka alone, but together with the bor zeriya the assumption is that all concerns are covered.[15]

Preparing for the Future

The above is a description of the basic stringencies adhered to by mikavos nowadays, although the truth is that there are many more. As large communities all use the same mikveh, legitimate effort is made to make sure it will be kosher enough for everyone.

However, in an era when the number of mikvaos needed will increase dramatically, it is hard to see how there will be enough space and money to provide for all these stringencies. It may well be necessary to 'take sides' in the various halachic disputes, and in preparation it is crucial that all these issues are studied in depth.

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[1] See Shemos 23:17, 34:23; Devarim 16:16.  Although women are exempt from coming to the Beis Hamikdash, they must come to Yerushalayim and take part in the celebrations (Yerushalmi Chagiga 1:2). According to the Rambam (Chagiga 1:1) this means partaking of the celebratory sacrifices, and even according to the Ra'avad who argues, taking part in the celebrations would have been impractical while ritually impure (although obviously not much could be done about it if it was the wrong time of the month).

[2] Mikvaos 7:7

[3] Sifra to Vayikra 11:36

[4] Bava Kama 67a, Bava Basra 65b

[5] Bava Basra 66b (דיבור ראשון). See Aruch HaShulchan, Yoreh Deah 201:14 who asks why one drasha in the Sifra is a real one, and one is only an asmachta (the two drashos appear in the same passage).

[6] Hilchos Mikvaos 4:1

[7] Ibid. 6:1-14. However, as yet I have not found anyone else who makes this obversation about the view of the Rambam. Many acharonim state that according to all opinions, immersion inside vessels is invalid according to Torah law.

[8] Mitzvah 173

[9] I believe that the possibility that all these leniencies (or some of them) were passed down orally to Moshe Rabbeinu (הלכה למשה מסיני) can be discounted, as there is not a single hint to this in the words of Chazal.

[10] Yevamos 82b

[11] See for example Rashi there. This is also the ruling of the Shulchan Aruch (Yoreh Deah 201:24).

[12] Rambam Mikvaos 4:7; Ra'avad, Sefer Ba'alei Hanefesh, Sha'ar 1. The Tashbetz (quoted by the Beis Yosef and Shach Y.D. ibid.) says that it is not correct to 'take sides' in this dispute, i.e. we should make sure that the mikveh is kosher even according to the stringent view.

[13] The Rambam (ibid. 4:6) is lenient in this case; the Ra'avad (ibid.) is stringent. The Chazon Ish (Yoreh Deah siman 123, paragraph 3) argues that the ruling of the Tashbetz not to 'take sides' does not apply here.

[14] Beis Yosef Yoreh Deah siman 201, based on Ramban Bava Basra 65a.

[15] Although the Chazon Ish (ibid. 4-5) argues that the bor hashaka does not help anything, as the water in it also gets replaced eventually. Furthermore, he claims that it can actually make the mikveh more problematic due to the measures necessary to ensure sanitation. Therefore he advises relying on the bor zeriya alone.

Mekach Ta'us

Introduction

Every legal system needs to define when the terms of a sale, employment contract or other transaction have been breached to the extent that the entire agreement is null and void. However, in Torah law there is an important distinction which to the best of my knowledge does not exist in common law. Apart from the right to terminate a contract that has been breached, it is often crucial to know whether the transaction was invalid from the outset. This is known as a mekach ta'us (mistaken sale).

For example, if a married couple discovered that the wife's wedding ring was worth much less than what they paid for it, they may have a right to return it to the seller and get a full refund.[1] If this is the case, it is likely that they will have a more serious problem. If the purchase of the ring was invalid, the result is that the man did not own it at the time that he used it for kiddushin. This invalidates the entire kiddushin, and they must go through this part of the marriage process again.

An important point to make here is that the above is true even if no-one is at fault. The couple may have lived together for years without noticing, and even the seller may not have known that the price was unfair (the value of gold may have dropped suddenly, or he might have mixed up two different rings).

A sale can be invalidated even because of unknown information unrelated to the thing being sold. The gemara tells us that if a person sold his property because of a desperate needs to raise funds during a famine, not realising that in fact that a huge shipment of wheat had arrived and prices would return to normal, he has the right to retract. In a place where famine is common, this right is abrogated out of concern that no-one will want to buy if the seller could easily retract.[2]

Unforeseen circumstances

What happens if all the information available at the time of purchase was known by both sides, but knowledge of events to come would definitely have stopped one side from going ahead? Obviously things like everyday changes in the stock market cannot justify annulment of trades, just like famine in a place where it is common. But what happens in freak circumstances?

The same gemara above concludes that even if the poor seller had no need for the money due to later events, the sale is null and void. However, Tosfos explain that this is only when the seller indicated at the time of sale that he was only selling in order to raise funds for something (which later became unnecessary). Such an indication is understood as a stipulation that the sale will only be valid if the money is needed.[3] The Rambam also explains that the case is when the seller stated explicitly that he is selling in order to raise funds for something specific. This statement is understood as a condition to the sale.[4] The Shulchan Aruch writes the same thing.[5]

From all this it seems clear that whenever a sale or other transaction is made without condition (explicit or implicit), it is not dependent on future events. This is presumably what most of us would have expected, as all agreements are made with the understanding that we can never know what exactly the future holds for us.

The case of theft with no-one to return to

In this light, we are faced with a difficulty when explaining a gemara elsewhere. To explain this we first need to explain a halacha which is unrelated at first glance. One who steals must return the stolen item (or if it is no longer extant, its value) to its rightful owner. If the owner has already passed on, the thief must return it to the inheritors of the person he stole from.

As every Jew has living family members if you look hard enough, there is only one possibility of someone with no inheritors- a convert who died without leaving children. One who stole from such a person would not ordinarily have to pay anyone, in the same way that an only son who stole from his father would not have to pay if his father died.

However, if the thief also denied his actions and swore falsely to that effect, he must always pay someone the amount that he stole plus 20%, as well as bringing a sacrifice to atone.[6] Even if he himself is the inheritor, he must give what he stole to the next in line to inherit.[7] If he stole from a convert who subsequently died and there is no inheritor, he gives the stolen property to the kohanim of the watch serving at the time.[8]

This obligation only applies to the one who stole himself. If the thief dies, his inheritors do not have to pay the kohanim. However, if the thief already paid, even if he died before bringing the sacrifice, his inheritors cannot get the money back.[9] The gemara discusses the reason for this.

Abaye claims that the money paid by the thief must have achieved a partial atonement for the theft. If this was not the case, the inheritors would have a valid argument to have the money returned- their father certainly only paid in order to achieve atonement. If this atonement was in the end not achieved, the payment is null and void.

The gemara questions this logic. Is it really true that a payment could be retroactively invalid due to the subsequent death of the payer and its implications? Following a similar argument, if a husband dies (without children) and his brother is a leper, the wife should be absolved from performing chalitza.[10] When she got married she never intended to be 'tied' to a leper!

The gemara answers that in fact when a woman gets married, she would be prepared to do so even if she was aware of the possibility of being 'tied' to a leper. This is because in general, women are willing to make sacrifices in order to get married.[11] Rashi explains that since her husband was unblemished, she was willing to marry him despite the risk of him dying and her becoming dependent on his brother.

The implication of this conclusion is that theoretically, a transaction can be null and void due to unforeseen events if we can be sure that it would not have been agreed upon with hindsight. Technically, this is not the case with a thief paying back money or a woman getting married to the brother of a leper, but in other circumstances it might be. How does this fit with what we have seen previously?

Is marriage different?

Tosfos ask the flip side of this question. If a transaction can be invalidated by unforeseen circumstances, any item purchased could be returned if it gets ruined subsequently! They answer that a sale cannot be invalidated through such a mechanism, as every sale involves two parties and the seller did want the sale to be valid even under the circumstances. Although marriage also involves two parties, the husband "is not concerned about her intentions."[12]

Seemingly, Tosfos are saying that a husband is willing to accept whatever conditions a wife has for marriage (even if they are not stated or even thought about at the time of marriage). This is a major assertion, although elsewhere Tosfos clarify why it is true in the case in question. As the marriage is only uprooted in the event of the death of the husband (as only then the wife becomes tied to his brother), the husband doesn't have much to lose.[13][14]

We can conclude from here that a transaction involving two parties can be declared null and void based on unforeseen circumstances. The criterion for deciding when this is the case is what would have happened had the question been raised at the time of the transaction. If there is a fair assumption that both sides would have agreed that the deal would be off under these circumstances, this theoretical agreement is enough.

Even if agreement would not have been achieved, if one side would have backed out from the transaction, this would logically be enough to annul it. Usually this is not the case, as people are aware that the way of the world is to lose out due to unforeseen circumstances and this is unpreventable. However, if one side subsequently takes advantage of his position to harm the other, this could be grounds for voiding the agreement. One obvious example is the case of a husband who abandons his wife immediately after getting married.[15]

This is not the case with the person who sells his property during a famine. One who buys property would not agree to have to return it just because the seller did not need the money in the end. Nor would the seller have insisted on this stipulation, as he could not afford to forgo this means of raising funds. Thus if no condition was hinted to (or at least consciously intended) at the time of sale, no future event can annul it.

Conclusion

In any case many factors need to be taken into account to decide whether agreement would have been achieved, and it is impossible to cover all of the possible permutations of different cases. But the estimation that needs to be made is always of the same nature. Would the party who stands to lose have been prepared to take this risk, in return for the gain he would have made under different circumstances?

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[1] The details can be complicated, and are set out in Choshen Mishpat siman 227. But the underlying principle is relatively simple: the transaction is invalid if most people would not have gone ahead with it had they known all the relevant information.

[2] Kesuvos 97a

[3] They quote another case, where a person sold his property and made it clear that he was planning to make aliya to Eretz Yisrael. The implication of the gemara in Kiddushin 49b-50a is that if this intention was stated at the time of sale, the sale is conditional on the move going ahead. They explain that although most conditions need to be clearly stated in order to take effect, sometimes a mere indication of a person's intentions makes is tantamount to an explicit condition. Elsewhere (Bechoros 51b ד"ה הלכך) they go further, implying that even an indication is not necessary. But even according to this view, the sale is only invalidated by the condition which we assume to be agreed upon by both sides.

[4] Hilchos Mechira 11:8

[5] Choshen Mishpat 207:3

[6] The extra 20% and the sacrifice apply to anyone who steals and swears falsely about it, see Vayikra 5:20-26 and Bava Kama 103b.

[7] Mishna Bava Kama 108b

[8] Ibid. 110a, based on Bamidbar 5:8. The kohanim were divided into twenty-four watches, who served bi-annually for a week at a time.

[9] Ibid.

[10] When a man dies without children, if he has a brother or brothers one of them must either marry his brother's widow (nowadays this option is discouraged) or perform chalitza (a ceremony where the widow removes her brother-in-law's shoe and spits, and both of them declare that he is not interested in marrying her. See Devarim 25:5-10.

[11] Bava Kama 110b-111a. Much has been written about whether or not this generalisation holds true nowadays, but this question is not relevant to our discussion.

[12] Ibid. (ד"ה דאדעתא)

[13] Although it may raise a retroactive question over the legitimacy of his marriage and relationship with his wife.

[14] Kesuvos 47b (ד"ה שלא).

[15] See this ruling which in this case arrives at the same conclusion, with slightly different reasoning (in other cases, these differences in reasoning lead to different results).