Bava Basra, Chapter 10, Mishnah 6. This Mishnah contains two unrelated sections: the first deals with a document that became blurred or erased, and how it is replaced so that it remains valid; the second section returns somewhat to the topic discussed in the previous Mishnah - how to proceed when the borrower repays his debt partially.
The First Section - An Erased Document:
"Mi shenimchak shetar chovo" - One whose document of debt was erased. Reuven lent money to Shimon and held a document of debt, but the document wore out, fell into water, or faded in the sun, and the writing is no longer legible. In this state, it is impossible to collect with it. However, the lender wants to collect his debt, and he has witnesses who can confirm the exact contents of the document: the date it was written, the amounts, the identity of the lender and borrower, and the rest of the important details.
"Me'idin alav eidim" - Witnesses testify about it. He must bring his two witnesses to testify on his behalf before a beis din. It is worth noting that this is the version of the text we have, whereas the Bartenura and the Rishonim have a different version: "He stands witnesses over it" ("ma'amid alav eidim"), meaning he provides his witnesses. These witnesses confirm what the contents of the document were before it was erased, destroyed, lost, or faded.
"Uva lifnei beis din ve'osin lo kiyum" - And he comes before a beis din, and they make a certification for it. The lender comes before the beis din with his worn document and with his two witnesses, and the beis din gives him a replacement document. "Kiyum" (certification) is from the word to establish or fulfill: a document that confirms what was written in the original document.
And the text of the certification document is: "Ish peloni ben peloni nimchak shetaro beyom peloni, upeloni upeloni eidav" - "So-and-so, son of so-and-so, his document was erased on such-and-such date, and so-and-so and so-and-so are his witnesses":
"Ish peloni ben peloni nimchak shetaro" - "So-and-so, son of so-and-so, his document was erased". This is the lender, our Reuven, who had a document in his possession and it was erased until it became illegible.
"Beyom peloni" - "On such-and-such date". The date recorded is not the date the certification document is written, nor the date the document was erased or washed away, as these are irrelevant. What is relevant is the date the original document was written, and this is a crucial detail: if the witnesses cannot ascertain this date exactly, the matter cannot proceed at all.
"Upeloni upeloni eidav" - "And so-and-so and so-and-so are his witnesses". The certification also specifies who the original witnesses were, so that if the borrower wishes to contest the document, he can turn to them and show that they are invalid.
In this way, Reuven can collect his debt, relying on the second set of witnesses that verifies the contents of the first document.
Why the Date is Critical:
When a person lends with a document, the borrower's real estate - his lands and things attached to the ground - are all placed under lien for the loan. If the borrower does not repay his debt, these assets that were in his possession at the time of the loan serve as security and collateral for repayment. Therefore, if the borrower meanwhile sold the property to a third party, the lender is permitted to approach the buyer and claim his debt from him, since his lien takes precedence. Thus, everything depends on the date: did the sale to the third party precede the loan or come after it. Because of this, the witnesses testifying for the certification must know the exact original date of the loan and testify about it.
The Second Section - Partial Repayment:
The second section of the Mishnah is disconnected from the first, and we return in it to the subject of the previous Mishnah, whose topic was asmachta (a conditional obligation). Here we discuss what is done when the borrower repaid his debt partially: Reuven lent Shimon one hundred, and Shimon returns only forty to him, leaving sixty to be paid. Two options stand before them, if they want everything to be legally backed by documents:
Replacing the document: They tear up the promissory note that has one hundred written in it, and write a new document in its place for the remaining balance of the loan - sixty. The disadvantage of this method: the new loan has a new, later date, the date of the partial payment. Thus, the lender loses the lien that goes back to the original loan, and his power is weakened.
Writing a receipt: The lender gives the borrower a receipt, which states that he returned forty on such-and-such date. If the lender later tries to collect the entire one hundred, the borrower will produce the receipt and prove that he already paid forty. The disadvantage of this method: the borrower must be extremely careful not to lose the receipt, for if he loses it, he will be forced to pay twice. In the days of the Mishnah, mice would gnaw at documents, and it could get lost or grow mold, putting the borrower at risk.
There is no option to backdate the new document, because an antedated document is completely invalid and the Sages do not rely on it at all. Even if the whole story is written in it in detail - that this is a second loan replacing the first, that there was an original loan of one hundred that was partially paid - it is of no use. The bottom line: the Sages do not accept documents written on a certain date that refer to a lien from an earlier date, as this is a recipe for disaster. Hence the great disadvantage of preparing a replacement document.
"Mi shepara miktzas chovo" - The borrower returned part of the loan, forty out of one hundred, and what should be done now? The Tanna'im disagree about this:
"Rabbi Yehudah omer yachalif" - We do not force the borrower to settle for receiving a receipt, and he has the right to demand a new document that only records the remaining amount. Even though this weakens the power of the lender, this is the halachah.
"Rabbi Yose omer yichtov shover" - We must favor the lender and not weaken his power, and therefore the lender should give a receipt to the borrower, and the borrower will be protected by it.
"Amar Rabbi Yehudah: nimtza zeh tzarich lishmor shovro min ha'achbarim" - Writing a receipt imposes an additional burden on the borrower, as he must guard his receipt from being eaten by mice and from getting lost, putting him at risk.
"Amar lo Rabbi Yose: kach yafeh lo, velo yura kocho shel zeh" - On the contrary, it is a good thing: the fear of losing the receipt puts pressure on the borrower to pay off his debt earlier, in full, and to settle the account before he loses his receipt. Writing a new document, however, would worsen the power of the lender, since he would no longer be able to collect from properties that were sold between the date of the original loan and the date of the new document. According to Rabbi Yose, the lender's rights must not be weakened in any way; rather, he should give a receipt, and the responsibility lies with the borrower to pay his debt on time and as quickly as possible.
In summary: In the first part of the Mishnah, we learned about a document that was erased - the lender presents witnesses before the beis din, and the beis din makes a ratification for him, a replacement document containing the name of the lender, the date of the original document, and the names of the witnesses, since the date is the foundation for the property lien and for collecting from purchasers. In the second part, we discussed a partial payment and the dispute between Rabbi Yehudah and Rabbi Yose - replacing the document or writing a receipt. The halachah follows Rabbi Yose: a receipt is written, and the responsibility to guard it is placed upon the borrower.