1) BELIEVING WITNESSES WHO WANT TO INVALIDATE A "SHTAR" THAT THEY SIGNED
QUESTION: Rav Nachman rules that when two witnesses who signed a Shtar testify later that the Shtar was a Shtar Amanah (that is, there was not really a loan), they are not believed. Similarly, when two witnesses who signed a Shtar testify later that, before they signed the Shtar, the seller declared a Moda'a in their presence and said that the transaction was done under coercion, they are not believed. Mar bar Rav Ashi argues and says that when they testify that there was a Moda'a, they are believed.
The RASHBAM (DH Ein Ne'emanim) writes that when the Gemara says that the witnesses are not believed to say that the Shtar they signed is a Shtar Amanah, this applies not only when the Shtar is Mekuyam (verified), but it applies even when the Shtar is not yet Mekuyam. The witnesses are not believed to say that the Shtar was an Amanah because of the principle of "Keivan she'Higid Shuv Eino Chozer u'Magid" -- once they have given testimony, they cannot change that testimony. Their signatures on the Shtar are considered their original testimony which cannot be altered afterwards. The Rashbam proves this from the Gemara in Kesuvos (18b). How, though, can the Rashbam prove this from the Gemara there? The Gemara there discusses a Shtar that is Mekuyam. If the Shtar is not Mekuyam, then the witnesses are believed to say that the Shtar is not valid, because the validity of the Shtar itself is based on their testimony and thus they are believed because of the principle of "Peh she'Asar Hu ha'Peh she'Hitir," as the Rashbam himself mentions later! (RASHASH)
(a) The RASHASH explains that the Rashbam is not proving from the Gemara that "Keivan she'Higid" applies when the Shtar is not Mekuyam. Rather, he is proving only that "Keivan she'Higid" applies to testimony that is written in a Shtar.
Why, though, does the Rashbam write that witnesses cannot say that the Shtar is an Amanah even if the Shtar is not Mekuyam, if the Gemara in Kesuvos says that they are believed because of "Peh she'Asar"? The answer is that the Gemara there gives credibility to the witnesses because of "Peh she'Asar" only when they do not diametrically contradict what is written in the Shtar. When the witnesses say that the Shtar was an Amanah, they contradict what is written in the Shtar, and therefore they are not believed (see TOSFOS DH Amar Rav Nachman).
(b) However, this does not seem to be the view of the Rashbam. In a few places, the Rashbam's words imply that when the Shtar is not Mekuyam, the witnesses are believed through "Peh she'Asar," and their second testimony is not invalid because of "Keivan she'Higid" (see Rashbam DH u'Mar bar Rav Ashi, and DH Moda'a Hayah Devareinu, where he writes that there is no "Peh she'Asar" because it is already known that the Shtar is valid because the lender and borrower both agree that it is valid). Moreover, Tosfos suggests this logic only to explain why "Peh she'Asar" does not apply according to his own view that Rav Nachman is discussing a Shtar that is not Mekuyam.
Therefore, it seems that when the Rashbam writes that the reason why the witnesses are not believed is "Keivan she'Higid," he is referring back to the case of a Shtar that is Mekuyam. Only later does he give the reason for why the witnesses are not believed when the Shtar is not Mekuyam, when he writes that the witnesses cannot give testimony that will incriminate themselves.
2) RELINQUISHING ONE'S RIGHTS TO RECEIVE A BENEFIT
QUESTION: The Gemara explains that the husband may relinquish his rights to the fields of his wife only by making a written statement to that effect ("Din u'Devarim Ein Li...") when she is still an Arusah. After they are married, it is too late for him to relinquish his rights, because the fields already belong to him with regard to their Peros. He cannot simply forgo his rights to the field; he must make a normal Kinyan and give the field away. (See Kesuvos 43a, "Yado k'Yadah.")
Why does the Gemara not explain that the husband relinquishes his rights to the Nichsei Melug after they get married, but before his wife inherits property from her relatives? Since that property was not yet in the possession of the husband, he should be able to forgo his rights so that the property will not become his when his wife inherits it!
(a) The ALIYOS D'RABEINU YONAH explains that the husband, after Nisu'in, indeed may forgo his rights so that he does not receive property that his wife inherits later. The Gemara could have suggested that case. When it says instead that the husband can forgo his wife's property only when she is an Arusah, it teaches the only way that he can forgo his rights to his wife's property (Nichsei Melug) which she owns at the time that they get married.
(b) The Yerushalmi in Kesuvos (9:1) cited by the ROSH (Kesuvos 9:1) implies that the husband cannot forgo his rights to property that his wife does not yet own, even when he writes "Din u'Devarim Ein Li" when she is still an Arusah. The reason for this is that the property is considered a "Davar she'Lo Ba l'Olam," and therefore the husband is not able to give it away. He can give away only property that his Arusah already owns.
(c) The RASHBAM (DH Ein l'Ish), however, writes that the laws described by the Gemara here refer even to property that a woman inherits while she is married. The Rashbam may have a different answer for why the Gemara does not suggest that the husband writes "Din u'Devarim" to relinquish his rights to his wife's property after the Nisu'in. The Rashbam (49b, DH ked'Rav Huna) explains that the husband has a reason for why he wants to relinquish his rights to the produce of his wife's property: he wants to exempt himself from his obligation to redeem his wife in the event that she is taken captive. TOSFOS (49b, DH Yecholah) points out that the Chachamim enacted that the husband has the right to eat the produce throughout the marriage in exchange for the obligation to redeem his wife in the event that she is taken captive. The enactment did not grant him the produce on a daily basis on condition that he accept upon himself the obligation to redeem his wife on that day. Hence, after the husband eats the produce for just one day, he may no longer exempt himself from the obligation to redeem his wife by not taking any more produce, because the produce that he already took obligates him to redeem his wife for as long as they are married.
This might explain why the Gemara wants to explain that the husband is ready to forgo his rights to the produce before the Nisu'in. (M. KORNFELD)
(d) TOSFOS and other Rishonim disagree with the Rashbam and maintain that the husband is obligated to redeem his wife even if he forgoes his rights to the Peros. The two Halachos are not interdependent.
The RAMBAN and RASHBA in Kesuvos (83a) give another reason for why the husband cannot relinquish his rights to the property that his wife will inherit after the Nisu'in. They explain that the reason why Rav Kahana allows a person to relinquish his rights only from an inheritance received through marriage and not from an inheritance d'Oraisa (such as inheritance that one receives from his father) is that a person has the rights to the inheritance from his father from the time he is born. Since he already has those rights, he cannot relinquish them (through "Siluk"), but he also cannot give the property away (through a Kinyan) since it is not yet his. The rights that a person attains through marriage are not his until the marriage, and thus before the marriage he can relinquish them such that he will not receive the property.
According to this approach, it is clear that once he marries her, the husband cannot give away his rights to property that his wife did not yet inherit, since the rights to inherit the property are already his, even though the property is not yet his. According to these Rishonim, there is no difference between rights that the Torah gives to a person and rights that the Chachamim give to a person. The reason why the Gemara mentions the Halachah of Rava -- that a person can forgo his rights to receive something through a Takanas Chachamim -- is to show that rights that are given by the Chachamim are not stronger than rights given by the Torah (for one might have thought that "Rabanan Asu Chizuk l'Divreihen"). The ROSH in Kesuvos explains that this is also the intention of the Yerushalmi.
The logic of the Ramban and Rashba, who say that a person cannot forgo rights that are already his, does not apply according to the Rashbam and Tosfos. They explain that the reason why a person can forgo a Takanas Chachamim made for his benefit is not that the Takanas Chachamim has not yet taken effect, but rather since the Takanas Chachamim was made for his benefit he is entitled to forgo the benefit. The same reasoning should apply even after the Takanah takes effect (for example, after the Nisu'in); the husband should be able to forgo his rights to receive the Peros by saying that he does not want to take advantage of the benefit that the Chachamim gave him. Therefore, the Rashbam must answer the question with one of the other answers mentioned above.
1) A WOMAN WHO SELLS HER FIELD IN ORDER TO PLEASE HER HUSBAND
QUESTION: The Gemara teaches that when a married woman sells her field to a buyer after her husband sold that field to the buyer, the sale is not valid. The woman can claim that she sold the field only in order "to please my husband" ("Nachas Ru'ach Asisi l'Va'ali") and that she did not really intend for the sale to take effect. The RASHBAM asks why should this case not be considered a case of one who is forced to sell a field (in this case the coercion element ("Ones") is the need to please her husband), in which case the sale is valid, as the Gemara earlier (47b) teaches? The Rashbam answers that when a woman sells her field under pressure to please her husband, that is not considered a significant form of coercion.
What does the Rashbam mean? If there is not a significant degree of coercion, then certainly her sale should be valid since she is considered to have sold it voluntarily! If, on the other hand, she indeed is considered to have been forced to sell the field, then the sale should be valid because she had full resolve in her mind to sell the field due to the coercion! (RAMBAN)
(a) The RAMBAN and other Rishonim disagree with the Rashbam and explain that when the buyer who purchases the field from the woman pays her the full value of the field (that is, what it is worth to her), the sale certainly is valid. The only time the sale is not valid is when he pays her less than the field's value, in which case she is able to claim that she sold the field only in order to please her husband.
(b) The AVNEI MILU'IM (90:27) explains that since the woman's goal is to please her husband, in order to accomplish that goal she needs only to sell the field to the buyer in such a way that the sale is effective while her husband is alive. Such a sale suffices to please her husband. Her husband will not be upset if the sale is done in such a way that the field reverts back to her ownership after he dies. (One may ask, however, what relevance does her sale have if it is effective only until her husband dies? Whether she agrees to the sale of the land or not, the buyer is able to eat the Peros of the field only until the husband dies! The answer is that when she sells the land until her husband dies, the buyer is entitled not only to the produce of the field, but he is also entitled to dig wells and pits and construct buildings on the land.) That the "Nachas Ru'ach" that the wife wants to do for her husband applies only during his lifetime is implied by the RA'AVAD (Hilchos Ishus 22:18). Accordingly, even if she does sell the field with full resolve in order to please her husband, the sale will not be effective after her husband's death because she did not intend to sell the field for after her husband dies.
(c) The Rashbam does not seem to follow these approaches. Perhaps the Rashbam understands that the rule that a forced sale is valid applies only when the seller is intimidated or humbled into selling his property by somebody else. In such a situation, he agrees to the terms of the one who forces him to sell. In contrast, in the case of the Gemara here the woman decides on her own that there is a need to please her husband and to show her consent to the sale, even though she does not actually want to sell the field. Therefore, since she is not humbling herself to the will of somebody else she does not resolve in her mind to sell the field. Nevertheless, her sale is still called an "Ones" because she is forced to pretend that she is selling it.