Shortly before Succos I was checking through esrogim at an esrog stand in order to find one that I liked. I picked up a seventy-five dollar esrog but I dropped it and it was seriously damaged. I told the esrog dealer what happened and wanted to pay him for the damage, thinking that I should pay the full seventy-five dollars. To my pleasant surprise the dealer replied that I should pay him twenty-five dollars since he had asked a rabbi who told him that he should take one-third of the sales price for damages. I paid what he asked and left. Was he correct and if not, do I now owe him money since he made a mistake?
We learned last week that the esrog dealer made a halachic mistake since the basis for his accepting twenty-five dollars instead of the seventy-five dollars you offered him is that he thought that the halacha only entitled him to that amount, when in fact it entitled him to around the seventy-five dollars you offered. Therefore, we must address your second question which is whether one who waives money that he is entitled to because he made a legal mistake in fact forfeits the money, or do we say that since it was based on a mistake the waiver was meaningless and he is still entitled to the money?
It would seem that this question was decided in the Gemara. The Gemara (BB 41B) tells an anecdote that involved an amora, Rav Onon. The wall demarcating the boundary between the property of R. Onon and his neighbor was swept away by a flood. R. Onon and his neighbor together constructed a new wall. They both made a mistake and constructed the wall somewhat into the neighbor’s property, effectively granting R. Onon a portion of his neighbor’s property. R. Onon was of the impression that since his neighbor participated in the construction of the wall, the neighbor effectively waived his ownership on that portion of his property. However, Rav Nachman corrected him that since it was mistake nothing transpired legally and R. Onon had to move the wall to the original place. Thus we see that when one mistakenly waives a right, it does not have any legal validity (mechilo beto’us lo havei mechilo). The rationale is that one must intend to waive a right in order for the waiver to be effective, as one must for any other transfer of ownership.
However, there is another Gemara that seems to contradict this conclusion. The Gemara (BM 66B) discusses one who sold the fruit of a tree before the fruit started growing. Since one cannot legally sell fruit before it starts growing (dovor shelo bo lo’olam) the sale is invalid. Nonetheless, the Gemara states that if the purchaser took the fruit after it grew because the seller mistakenly thought that the sale was valid, he may keep it since the seller waived his right to prevent him from taking the fruit. Here we see that even though the seller only waived his right to the fruit because he erred, nevertheless the waiver is effective. This seems to contradict the previously cited Gemara.
This question is raised by Tosafos and many other Rishonim. Tosafos answers that we assume that the seller would waive his rights to invalidate the sale even if he found out that the sale was ineffective since by doing so he creates a feeling of mutual trust. Therefore, one cannot compare this situation with the case of the neighbor who mistakenly agreed to move the boundary, who has no such reason to allow his error to remain.
The Rivash (res 335) cites Rabbeinu Tam as offering a different resolution. He says that the difference is that in the case of the boundary the neighbor never intended to waive anything. He just mistakenly thought he was building the wall in the proper place when in fact he wasn’t. Thus his entire action was a mistake. However, in the case of the fruit, the seller fully intended to sell the fruit to the purchaser. His mistake was because the cause of his agreement was a legal error. However, the action itself was not an error. The Ketsos (17, 3) claims that this is the approach of the Rosh (BM 5, 32) as well.
In another case involving a mistake the Rama (CM 17, 12) rules that if a dayan notices that a plaintiff actually is entitled to more than what he is claiming in his din Torah, the dayan is not allowed to correct the plaintiff. Moreover, should the dayan award the plaintiff the amount he really is entitled to, the ruling is null and void. One of the sources cited by the Rama is another responsum of the Rivash (227). The commentaries on the Rama find his ruling very difficult since people generally want everything they are entitled to and presumably the only reason the plaintiff failed to ask for the larger amount is because he wasn’t aware of what he was entitled and, as we saw earlier, when one waives a right in error it is ineffective.
The Ketsos (17, 3) answers that the Rivash (227) on which the Rama based his ruling is in accordance with his approach (335) that we studied before: when the cause of a person’s mistake is lack of legal knowledge his action is nonetheless binding. Therefore, when the plaintiff did not claim something he was entitled to, he effectively waived his claim and he was no longer entitled to it. Therefore, if the dayan awards him a claim he did not make, the dayan would be mistaken because the plaintiff was in fact no longer entitled to that claim.
The Nesivos (17, 1) disagrees both with the answer of the Ketsos and with his interpretation of the Rama’s ruling. He asks that the Gemara (BM 66B) states that the reason the Torah requires a seller who overcharged to return the overcharge (if the discrepancy is great enough) is because the customer only overpaid because he was unaware of the fair price and therefore, the seller is not entitled to keep the overcharge. The Nesivos argues that there is no basis to differentiate between a mistake based on lack of factual knowledge and a mistake based on lack of legal knowledge, since the determining factor of whether an action is valid is if the person acted on the basis of a mistake or not. He says that the Rama agrees that in case a plaintiff is entitled to more money than he is claiming the dayan is obligated to correct his mistake. He claims that the Rama only rules that a dayan may not interfere if the plaintiff will not forfeit any money as a result of his ignorance.
The Yeshu’as Yisro’ail (17, 3) sides with the Nesivos. He argues that when the Rivash and subsequently the Rama ruled that a decision based on legal ignorance remains valid, they only referred to cases that are similar to the sale of fruit that was cited previously. In the case of the fruit the owner really wanted to sell the fruit to the customer. He merely erred in not acting in a legally effective manner. Since he desired to sell the fruit, we rule that his failure to take advantage of a legal option because of his ignorance does not invalidate the sale. However, if from the very beginning his action was based on a mistake and he never really desired to waive anything, his waiver is not valid.
We should note further that the Shach (17, 15) also is certain that there is no legal validity to a waiver that is based on legal ignorance. He claims that even the Rama never intended such a ruling. The basis for this interpretation is the wording of the Rama in a different section (241, 2), “Any waiver that was made in error is invalid.” Furthermore, there are commentaries who understand that even the Ketsos only intended to explain the Rivash in this manner, but he himself really agrees that a waiver of a right that is due to ignorance of the law is invalid.
Thus, your question whether the seller’s waiver was effective is at best the subject of a dispute, since in your case the seller never desired to accept anything less than what he was entitled to. It was only due to a legal mistake that he agreed to accept twenty-five dollars and not the seventy-five dollars he was entitled to. According to the Ketsos’ understanding of the Rivash you do not owe him any money but according to the Shach, Nesivos and Yeshu’as Yisro’ail and perhaps even the Ketsos himself, you owe him around fifty dollars. (We explained the way to compute the exact amount in the first section of this article.)
We asked Rav Naftoli Nussbaum and he also ruled that you may not keep the difference based on this Ketsos since his rationale is very strained and is disputed by most poskim.