Sotah 20B

חוץ מפרשת סוטה בלבד. רבי יעקב אומר משמו: חוץ מפרשת סוטה של מקדש. מאי בינייהו? אמר רבי ירמיה: למחוק לה מן התורה איכא בינייהו.

except for the ink used to write the Torah passage about the sota, even when written in a Torah scroll. R' Ya’akov says in the name of R' Meir: It is except for the ink used to write the scroll with the sota passage used in the Temple. The Talmud asks: What is the difference between these two opinions? The Talmud replies: R' Yirmeya says that there is a difference between them with regard to whether it is permitted to erase the passage for the sota from a Torah scroll. According to R' Yehuda, R' Meir holds that this is permitted, and therefore the passage in the Torah scroll must be written with ink that does not contain iron sulfate, so that it can be erased. By contrast, according to R' Ya’akov, R' Meir holds that it is prohibited to erase the passage from a Torah scroll, and therefore the passage may be written with ink containing iron sulfate.

והני תנאי כי הני תנאי. דתניא: אין מגילתה כשירה להשקות בה סוטה אחרת. רבי אחי בר יאשיה אומר: מגילתה כשירה להשקות בה סוטה אחרת.

The Talmud assumes that according to R' Ya’akov it is prohibited to erase the passage from a Torah scroll, since he holds that the scroll must be written for the sake of the sota, whereas R' Yehuda, who permits this, holds that the scroll need not be written for the sake of the sota. And therefore, the opinions of these tanna’im are parallel to the opinions of those tanna’im, as it is taught in a baraita: The scroll of one sota is not fit to be used in the preparation of the water to give to another sota to drink, as it was not written for the sake of the other sota. R' Aḥai bar Yoshiya says: Her scroll is fit to be used in the preparation of the water to give to another sota to drink, since it does not need to be written for the sake of the sota.