1) ARGUING A CASE IN COURT FOR SOMEONE ELSE
QUESTION: The Gemara teaches that if Reuven sells a field to Shimon with Achrayus, and then Reuven's lender comes and tries to take the field from Shimon, Reuven may defend Shimon's case in court in order to stop the lender from collecting the land from Shimon, since Shimon's loss ultimately will affect Reuven as well.
What difference does it make whether Reuven comes to court or not? If there is a valid claim which can prevent the lender from collecting the land, why can Shimon not use that claim without bringing Reuven to court? (Reuven could tell Shimon the claim out of court and let Shimon make the claim himself in court.)
ANSWERS:
(a) RASHI here (and in Kesuvos and Bava Kama) explains that the reason why Reuven would have to come to court is that he has a claim of certainty ("Bari") against the Malveh's Shtar. Shimon, who does not know the details for certain, can make at best a tentative claim ("Shema") and say that "I think that the Shtar is not valid (because Reuven paid you or because you owed money to Reuven for some other reason and therefore he was entitled to withhold payment for this debt)." A claim of "Shema" has no validity against a Shtar. In contrast, Reuven's claim of certainty ("Ta'anas Vadai") carries weight against a Shtar. The Rabanan instituted a Shevu'as Heses for one who challenges a claimant who has a "Ta'anas Vadai." Therefore, Reuven can cause the Malveh to swear a Shevu'as Heses in court, while Shimon cannot.
TOSFOS RABEINU PERETZ asks, why is it necessary for Reuven to cause the Malveh to swear a Shevu'as Heses? The Malveh must swear to Shimon anyway, before he may collect from him, because the Rabanan instituted a different Shevu'ah which requires anyone who collects a debt from Yesomim or Lekuchos to swear that he was not paid already for the debt. (The Rabanan require Beis Din to speak up on behalf of the Lekuchos, who are not expected to know how to counter the claim. Thus, Beis Din automatically imposes a Shevu'ah on anyone who comes to collect from Lekuchos.)
TOSFOS in Kesuvos (92b) answers that the difference that Rashi gives for when Reuven makes the claim instead of Shimon (i.e. the ability to make the Malveh swear a Shevu'as Heses) will apply in a case in which Shimon pardoned to the Malveh the Shevu'ah of Lekuchos. In such a case, only Reuven can make the Malveh swear, through a "Ta'anas Vadai" which obligates him to make a Shevu'as Heses.
(b) TOSFOS explains that the difference might be in a case in which Shimon announces in court that he has no evidence to disprove the claim of the Malveh. If he does try to bring evidence afterwards, Beis Din cannot accept it (Sanhedrin 31a). On the other hand, Reuven never announced that he had no witnesses, so he still may bring witnesses to court to disprove the Malveh.
(c) The RASHBA and NIMUKEI YOSEF (in Bava Kama) and the RAN here explain that Shimon would need Reuven to make the claim for him in court in a case in which the land that Shimon bought is an Apotiki for a loan. The Halachah is that a buyer cannot pay with money to redeem land that is an Apotiki for a loan. Rather, the Malveh is entitled to take the land itself. The borrower himself, however, may redeem the Apotiki by paying money for the loan that he received, and he thereby can prevent the Malveh from collecting the Apotiki. Therefore, if Reuven comes to court and says that he will pay back the loan to the Malveh, he can prevent Shimon from losing the property.
However, if this is the case, why is Reuven, the borrower, permitted to become involved in the case for the benefit of Shimon? The Gemara explains that Reuven is permitted to become involved because Shimon's loss affects him, since he will need to reimburse Shimon if the land is confiscated. If Reuven agrees to pay the loan, then it should make no difference to him whether Shimon wins the case or the Malveh wins; in either case he will have to pay someone back -- either the Malveh or Shimon!
They answer that it is still to Reuven's benefit for Shimon not to lose his land, because when a Malveh collects land, the land is assessed at the value that it was worth at the time that Shimon purchased it. If it naturally rises in value (without Shimon investing anything in it) before the time that the Malveh takes it from Shimon, then the Malveh keeps the profit. Shimon, however, may demand from Reuven, the borrower, full reimbursement of his loss, including the additional value. Therefore, if Shimon loses the field, Reuven will have to pay more to reimburse Shimon than he would have to pay to the Malveh.
(d) TOSFOS here suggests further that there would be a difference in the case of a Gilgul Shevu'ah. If, because of some different case in which they are involved, the Malveh needs to make a Shevu'ah d'Oraisa to Reuven, the borrower, then Reuven may insist that the Malveh make a Shevu'ah d'Oraisa that he did not yet receive the loan repayment, through the Halachah d'Oraisa of "Gilgul Shevu'ah." This will make the Shevu'ah more severe than a Shevu'ah d'Rabanan, and therefore it is to Shimon's benefit for Reuven to come to court.
The ME'IRI cites others who suggest in a similar vein that the practical difference would be in a case in which Reuven has other claims for which he wants to make the Malveh swear. If Reuven represents this case for Shimon, then he may make the Malveh swear to his other claims as well through the Halachah of Gilgul Shevu'ah (d'Rabanan). (According to the Me'iri, however, Reuven would be coming to court for his own benefit, and not for Shimon's benefit as the Gemara implies.)
(e) TOSFOS RABEINU PERETZ and TOSFOS here explain that it would be beneficial for Reuven to come to court if Reuven is more knowledgeable than Shimon and he might think of a claim that Shimon might not think of. Why, though, is this a reason for Reuven to come to court? Reuven should simply make suggestions to Shimon, who would then make the claims for himself!
Perhaps the court would not let Reuven advise Shimon in the middle of the case, because the Mishnah in Avos (1:8), cited in Kesuvos (52b), teaches that a person should not act like "Orchei ha'Dayanim."
Tosfos here suggests further that a person may insist that his opponent come with him to a greater Beis Din. If Reuven has the strength to go to a greater Beis Din, and Shimon does not have the strength, then Reuven may insist that the Malveh go with him to a greater Beis Din.
Finally, Tosfos suggests that it is beneficial for Reuven to argue the case in Beis Din because the Malveh might not be so brazen as to lie to Reuven's face and say that he was never repaid, whereas he would be brazen enough to lie to Shimon and say that he was never repaid, since Shimon does not know the truth.
(f) The RITVA upholds one of the differences which Tosfos here refutes. One might have suggested that Reuven would need to go to court when the witnesses who can testify that the loan was repaid are relatives of Shimon but not relatives of Reuven. In such a case, Shimon would not be able to bring those witnesses to court, but Reuven would be able to bring them. Tosfos asserts, however, that since the outcome of their testimony will also benefit Shimon (by allowing him keep the land that he bought from Reuven), these witnesses may not testify even for Reuven. Tosfos proves from the Gemara in Makos (7a) that the witnesses in such a case -- where their testimony is given primarily for an unrelated person, but it will affect a relative -- may not testify for the unrelated person. The Gemara there discusses a case of a debt in which the witnesses who testify on behalf of the borrower were related to the guarantor of the borrower. The Gemara there says that the witnesses are disqualified in that case and may not testify on behalf of the borrower or the lender, because if the borrower has no money to pay back the debt, the lender will collect the money from the guarantor.
The Ritva, however, disagrees with Tosfos and makes a distinction between this case and the case in Makos. In the case in Makos, the guarantor's property is also Meshubad to the loan, and thus when the witnesses testify about the loan their testimony directly affects the guarantor. In contrast, in the case of the Gemara here, Shimon -- who bought the field from Reuven -- has no connection to the loan, and his property is not Meshubad to the loan. The witnesses, therefore, would be permitted to testify that Reuven paid back the loan, even though as a result of that testimony Shimon, their relative, will be able to keep the land that he bought from Reuven. Their testimony is about the repayment of the loan, which has no connection to Shimon. Therefore, it indeed makes a different whether Reuven goes to court against the lender or Shimon goes to court.

14b----------------------------------------14b

2) A CREDITOR'S RIGHT OF APPROPRIATION OF PROPERTY FROM A PURCHASER
OPINIONS: Rav Nachman in the name of Shmuel rules that the purchaser of a stolen field is not entitled to collect the "Shevach," the value of the improvements that he made in the field, from the thief who sold the field to him. He may collect only the money that he paid for the field. The Gemara questions this ruling from a Beraisa which states that one may not collect "Shevach Karka'os" from Nechasim Meshubadim, which implies that one may collect it from Nechasim Bnei Chorin. The Gemara assumes that the Beraisa refers to the Shevach produced by the purchaser of a stolen field, and thus the Beraisa contradicts the ruling of Rav Nachman in the name of Shmuel.
The Gemara answers that the Beraisa does not refer to the Shevach of the purchaser of a stolen field, but rather to the Shevach of a field that one bought from a borrower and that was then collected by the creditor (Ba'al Chov). In that case the Beraisa says that the purchaser is entitled to collect the value of the Shevach from the seller (i.e. the borrower).
The Gemara asks that the Beraisa cannot refer to land appropriated by a Ba'al Chov because the Reisha of the Beraisa says that a purchaser whose field was confiscated may not collect the "Achilas Peros," the value of the consumption of the produce, from the seller's Nechasim Meshubadim, which implies that he may collect it from the Nechasim Bnei Chorin. However, Shmuel himself rules that when a Ba'al Chov appropriates a field from one who purchased it from his debtor, he collects the field together with the field's Shevach, but he may not collect the Peros of the field. Hence, the purchaser obviously will not be collecting the Peros from the seller, since the Peros were not taken from him. The Gemara concludes that, indeed, the Reisha ("Achilas Peros") does not refer to the case of a Ba'al Chov but rather to the case of one who purchased a stolen field from a thief, while the case of "Shevach Karka'os" refers to a Ba'al Chov.
When Shmuel states that a Ba'al Chov is not entitled to take the Peros grown on his land by the purchaser, to what Peros does his statement refer?
(a) RASHI (DH l'Achilas Peros) explains that the Ba'al Chov may not collect the fully-grown Peros which are still attached to the ground but which no longer need to be attached (that is, they no longer depend on that attachment). Rashi implies that Peros which still need to be attached to the ground are collected by the Ba'al Chov.
According to Rashi's explanation, however, the Gemara could have answered its question from the Reisha of the Beraisa in a more simple way. The Gemara could have said that the Reisha indeed discusses a case of a Ba'al Chov, and when it implies that the purchaser may collect the value of the Peros that were confiscated from him, it refers to the young Peros that still need to be attached to the ground.
The Rishonim (RAMBAN, RASHBA, and others) answer that the Gemara could not have given this answer because such Peros are included in the Shevach of the field, and they would not be referred to separately as "Achilas Peros."
The Ramban and Rashba maintain that the Rif agrees with Rashi.
(b) Some Rishonim, such as the RITVA, interpret the opinion of the RIF differently. They understand that the Rif maintains that the Ba'al Chov may collect the land even with Peros that do not need to be attached to the ground but are still attached. When the Gemara states that the Ba'al Chov may not collect the Peros, it refers to Peros that are detached already from the ground. (Although there is a principle that "anything which is [attached to the ground but is] ready to be picked is considered picked already," this principle applies only to giving the Peros a status of Metaltelin as opposed to a status of Karka. The purchaser of the land, however, is not entitled to keep them, unlike Peros that have already been detached, for these Peros belong to the Ba'al Chov.)
(c) Another view is cited in the name of RAV HAI GA'ON. This view states that even Peros that are attached to the ground and depend on their attachment to the ground may not be collected by the Ba'al Chov. Why may the Ba'al Chov not collect them? If they need to remain attached to the ground, they should be considered part of the field and the Ba'al Chov should be able to collect them!
The SHACH (CM 98:9) writes that since the purchaser has the ability to pick the Peros, the Ba'al Chov does not have them in mind (to collect the debt from them) at the time of the loan. (I. Alsheich)

OTHER D.A.F. RESOURCES
ON THIS DAF