[If] someone's loan document was erased, witnesses attest to it, and he comes before the court and they draw up a validation: The document of so-and-so, the son of so-and-so, was erased, of such and such a date, and so-and-so and so-and-so were his witnesses.  [If] one paid part of his debt, R' Yehudah says: He should exchange [the document]. R' Yose says: He should write a receipt. Said R' Yehudah: This results in his needing to safeguard his receipt from the mice. R' Yose said to him: It is fit-ting for him, so that this one's position not be impaired.