1) REBBI YOSI'S REASON FOR THE WRITING OF A "SHOVER"
OPINIONS: The Beraisa records two opinions in the case of a borrower who pays part of a debt written in a Shtar Halva'ah. Rebbi Yehudah rules that the original loan document should be torn up, and the witnesses should sign a new Shtar with the new amount owed, and date it from the day that the original loan was given. Rebbi Yosi says that the original Shtar is kept by the lender, who writes a receipt for the partial repayment that the borrower paid.
Rebbi Yosi gives two reasons for his position. His first reason is that as long as the original Shtar is in existence, the borrower will be forced to pay back all of the money. His second reason is that the original Shtar enables the lender to collect the debt from Nechasim Meshubadim from the original date of the loan, and not from a new date. The Gemara asks that even Rebbi Yehudah says that the new Shtar should contain the old date, and thus how does Rebbi Yosi differ from Rebbi Yehudah? The Gemara concludes that Rebbi Yosi adds this reason only because he is unsure of whether Rebbi Yehudah agrees that the new Shtar should show the original date.
The Gemara seems to conclude that Rebbi Yosi's primary reasoning is that the original document will force the borrower to pay back the money. How will the original document force the borrower to pay back, any more than a new document?
(a) The RASHBAM (DH Kedei) explains that the borrower is afraid that he might lose the receipt, and the lender will claim (either mistakenly or maliciously) the entire amount of the original loan. This motivates the borrower to repay the entire amount as soon as possible so that he will get possession of the original Shtar.
(b) The RAN adds that if Beis Din encourages the practice of writing new Shtaros, the borrower might pay back most of the money and then neglect to pay back a small amount which he still owes. When the Shtar with the entire debt is left in the hands of the lender, the borrower makes sure to pay back all of the money, since he is afraid that the lender eventually will claim all of the money from him.
(c) The NIMUKEI YOSEF explains that if new Shtaros are written, the borrower will feel secure that he may continue to pay back the loan little by little. This practice hurts the lender, who needs his money back all at once (the same way he lent the borrower the money all at once).
(RASHI in Kesuvos (56a, DH Rebbi Yosi) also explains Rebbi Yosi's reasoning. However, he gives only the second reason mentioned by in the Gemara here, that Rebbi Yosi wants to ensure that the date is the original date so that the lender may collect from that date from Nechasim Meshubadim. TOSFOS there (DH Rebbi Yosi) asks the obvious question: Rashi seems to ignore the conclusion of the Gemara here in Bava Basra, that the real reason of Rebbi Yosi is to encourage the borrower to pay, and not because of the date of the Shtar. Why does Rashi ignore the conclusion of the Gemara here? See the HAFLA'AH to Kesuvos there, who explains that the reason of forcing the borrower to pay back is not as applicable in the case of a Kesuvah as it is in the case of a loan.) (Y. MONTROSE)
2) WHY LOSING A "SHTAR" MIGHT RESULT IN BEING UNABLE TO COLLECT
QUESTION: The Mishnah and Gemara earlier discuss the various opinions among the Tana'im in the case of a partial repayment of a loan. The Tana'im disagree about whether a receipt is written, or whether the original Shtar is replaced by a new one. The Gemara here adds that even according to Rebbi Yosi, who maintains that a receipt is written for a partial repayment of a loan, one does not write a receipt for a full repayment. Rather, the lender is responsible to give back the Shtar when the borrower repays the loan. What is the Halachah in a case in which the lender claims that he lost the Shtar or that it was destroyed? In such a case, is he unable to collect the loan? The Gemara says that this is the subject of dispute among the Amora'im. Rav and Shmuel rule that the lender cannot collect the loan in such a case. Rebbi Yochanan and Reish Lakish rule that the lender may collect the loan by writing a receipt to indicate that he received payment.
Apparently, Rav and Shmuel are concerned that the lender (or his heirs) eventually will find the Shtar and will claim (either mistakenly or maliciously) the money again from the borrower, who might have lost the receipt. For this reason they rule that a lender who loses his Shtar cannot collect his money. The Gemara implies that the Halachah follows the view of Rebbi Yochanan and Reish Lakish.
The NESIVOS HA'MISHPAT (CM 54:1) writes that the opinion of Rav and Shmuel is very difficult to understand. A person who lends money and takes a collateral from the borrower is considered a Shomer Sachar on the collateral. If armed bandits come and steal the collateral, the lender may exempt himself from liability for the collateral by taking an oath and attesting to what happened. This is because armed bandits are considered an "Ones" for which a Shomer Sachar is exempt. The lender, however, still collects his loan. If the borrower still must pay the lender when the lender did not secure something of monetary value (collateral) of the borrower, why should the borrower not have to pay when the lender merely lost the Shtar?
ANSWER: The NESIVOS HA'MISHPAT answers that this opinion maintains that collateral differs from a Shtar. Collateral is not actually a direct part of the loan. The borrower merely gives collateral to ensure that he will pay back money, which is not from the collateral itself. The Shtar, in contrast, considered the body of the loan, and its return to the borrower is conditional for repayment of the loan.
Why is the Shtar so critical? The Nesivos ha'Mishpat quotes the KENESES HA'GEDOLAH (82, Klalei Migu #57) who writes that a valid Shtar in the hands of a lender is considered as good as collected, since the Shtar creates a lien on the land of the borrower which remains in effect as long as the lender owns the Shtar. This active lien in the Shtar needs to be given back to the borrower, and thus the borrower is exempt from repaying until the lender gives him back the Shtar (unless there are witnesses that the Shtar was burned, in which case the Shtar is not in danger of being found and used again). (Y. MONTROSE)