Gittin 22B

רבי אלעזר היא, דאמר: עדי מסירה כרתי.

It is the opinion of the tanna R' Elazar, who says: Witnesses of the transmission of the bill of divorce effect the divorce. Since the witnesses read the bill of divorce before it is transmitted in their presence, they may be relied upon to confirm the contents of the bill of divorce in court. Therefore, even if it was written on erased paper, there is no possibility that it would be forged, as the witnesses read what was written before it is given.

ואמר רבי אלעזר: לא הכשיר רבי אלעזר אלא לאלתר, אבל מכאן עד עשרה ימים ⁠– לא; חיישינן דילמא הוה ביה תנאה וזייפתיה.

And the amora R' Elazar says: The tanna R' Elazar deemed such a bill of divorce valid only when it was taken to court in order to confirm the contents immediately after it was transferred to the woman. However, if the witnesses testify from now until 10 days, i.e., sometime later, he did not deem it valid. Why? We are concerned that perhaps the bill of divorce had a stipulation written on it and she forged it by erasing the stipulation, as this bill of divorce was written on material that enables a person to easily alter what is written. Only if the witnesses testify immediately can the court be sure that they did not forget what is written.

ורבי יוחנן אמר: אפילו מכאן עד עשרה ימים; דאם איתא דהוה ביה תנאי ⁠– מידכר דכירי.

And R' Yoḥanan says: Even if they testify from now until 10 days it is valid, as, if it is so that it had a stipulation, then the witnesses will remember it, as they would not forget something so obvious. Therefore, if the woman erased the stipulation, the witnesses would not verify the bill of divorce.