Bava Batra 170B

אמר אלא לברר! אמר ליה: אנא נמי ⁠– לברר קאמינא.

say that the litigant loses the case if he cannot produce verification of his extraneous claims, but only that he is told to verify those claims if he can. R' Yitzḥak Nappaḥa said to R' Abba: I, too, am saying only that you are required to verify your claim if you can; if you cannot, you will not be required to pay.

מתני׳ מי שפרע מקצת חובו, רבי יהודה אומר: יחליף, רבי יוסי אומר: יכתוב שובר. אמר רבי יהודה: נמצא זה צריך להיות שומר שוברו מן העכברים! אמר לו רבי יוסי: כך יפה לו, ולא ירע כחו של זה.

Mishnah: In the case of a debtor who repaid part of his debt, R' Yehuda says: The creditor should exchange the promissory note for a new one stating the current balance and tear up the first promissory note. R' Yosei says: The creditor may keep the original promissory note, and he should write a receipt for the payment he has received and give it to the debtor as proof of his partial payment of the sum recorded in the old note. R' Yehuda said with regard to this arrangement: It is found that this debtor must now guard his receipt against being destroyed by mice, as if he no longer has the receipt, he will have to pay the entire sum recorded in the promissory note. R' Yosei said to him: This situation is fitting for him; it is better that this procedure be followed, and the strength of the claim of this creditor not be weakened.

גמ׳ אמר רב הונא אמר רב: אין הלכה לא כרבי יהודה ולא כרבי יוסי; אלא בית דין מקרעין השטר, וכותבין לו שטר אחר מזמן ראשון.

Talmud: Rav Huna says that Rav says: The halakha is not in accordance with the opinion of R' Yehuda, nor is it in accordance with the opinion of R' Yosei. Rather, the halakha is that the court tears up the original promissory note and writes a different promissory note for the creditor, listing the new sum owed, dated from the time of the first document.