Study Bava Batra folio 171A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
Granted, a court can write a new document, because the court has the power to confiscate money. A creditor has the right to seize any property that the debtor had owned on the day the promissory note was written, even if that property was subsequently sold to others; the earlier the date on the note, the more properties it applies to. By dating the new document on the date of the original document the creditor is once again given the right to seize properties from those who had purchased land from the debtor in between the date of the original loan and the date the new promissory note is actually written. The court has such confiscatory power. But with regard to witnesses, who already performed their agency, i.e., fulfilled their assigned role, the first time they wrote the promissory note, can they return and perform their agency again by writing a second promissory note?
ולא?! והא אמר רב יהודה אמר רב: עדים כותבין אפילו עשרה שטרות על שדה אחת!
The Talmud asks: And is it so that witnesses are not empowered to do so? But doesn’t Rav Yehuda say that Rav says: Witnesses who were commissioned to write a deed for the transfer of property may write even 10 deeds for one field? If the original deed is lost or destroyed, the witnesses may write a replacement deed for the purchaser, even if the deed is lost many times.
רב יוסף אמר: בשטר מתנה,
Rav Yosef says an answer to this question: Rav Yehuda’s statement was concerning a deed of gift, not a bill of sale. A gift of land has no guarantee; if it is repossessed from the recipient by the giver’s creditor to repay the giver’s debt, the recipient has no recourse and cannot collect any money from anyone. Therefore, in this case no one is jeopardized by the writing of many replacement deeds, which are intended only to serve as a proof that the recipient is actually entitled to the land.