Bava Metzia 13A

בשטרי הקנאה, דהא שעביד נפשיה.

This Mishnah is referring not to one who finds an ordinary promissory note but to one who finds deeds of transfer. This refers to a promissory note that establishes a lien on the debtor’s property from the date the note is written, regardless of when he borrows the money. Because the debtor obligated himself from that date, the creditor has the legal right to repossess his land from any subsequent purchasers.

אי הכי, מתניתין דקתני: ״אם יש בהן אחריות נכסים לא יחזיר״, ואוקימנא כשחייב מודה, ומשום שמא כתב ללות בניסן ולא לוה עד תשרי, ואתי למטרף לקוחות שלא כדין, אמאי לא יחזיר?

The Talmud asks: If that is so, the following difficulty arises: How will one account for the ruling of the Mishnah here, which teaches that if the promissory notes include a property guarantee, the finder should not return them to the creditor; and we established that the reference is to a case when the debtor admits that he still owes the debt and that the promissory note should not be returned due to suspicion that perhaps the debtor wrote it with the intention to borrow the money in Nisan but did not actually borrow it until Tishrei, and therefore, if the promissory note is returned to the creditor he will come to repossess the land from the purchasers unlawfully. If Rav Asi’s explanation is correct, why shouldn’t the finder return the document?

נחזי אי בשטר הקנאה ⁠– הא שעביד ליה נפשיה! אי בשטר דלא הקנאה ⁠– ליכא למיחש, דהא אמרת כי ליכא מלוה בהדיה לא כתבינן.

The Talmud elaborates: Let us see what the possibilities are. If the reference is to a deed of transfer, didn’t the debtor obligate himself that his property can be collected for payment of the loan from the date that the deed of transfer was written? Conversely, if the reference is to a promissory note that is not a deed of transfer, there is no room for concern, as you said that in such a case, when the lender is not present together with the borrower, we do not write such a document.