Nazir 51 - 57
It was taught in a beraita, “His teeth became black as a result of his fasts”.
The context of this statement is that Rabbi Shimon spoke about his Torah teacher — Rabbi Akiva — in a manner that was lacking appropriate derech eretz and respect. “Did he (Rabbi Akiva) change his mind after he died?” asked Rabbi Shimon rhetorically. As a result, Rabbi Shimon fasted for many days, which had a negative physical impact on him, but was part of his atonement process. (Rashi, Tosefot)
- Nazir 52b
“When a Torah teaching is being taught in a long chain of tradition, only two names must be mentioned: the name of the first Sage who said it, and latest Sage it was heard from.”
The gemara on our daf shows that this is evident from the sugya, and also brings a proof from a mishna in Tractate Pe’ah (2:6) which omits the Sages Yehoshua ben Nun and Kalev ben Yefuneh in listing the chain of transmission of the teaching. Although more than the names of the first and final Sages are mentioned, the commentaries explain that this is permitted despite not actually being required.
- Nazir 56b