I had intended to record my notes on Gittin 36 through 38, but there’s so much on 36 alone that I have to settle for that. If you have the patience, and access to a gemara, you may find some of these interesting.
Ordinarily, a vow taken “על דעת רבים - on the mindset of the community” cannot be nullified, for the mindset of the individual taking the vow, and any subsequent regret he feels, is irrelevant. Here, though, we say that such a vow may be revoked for the sake of a mitzvah. Tosafot explains that the community, it may be assumed, does desire that the mitzvah take place. Further, he says it is not a reference to the community in general, but rather to specified individuals - who could, I suppose, be polled for their approval.
However: What is the mitzvah in our case?!
The gemara mentions דיסקי as one way in which people would recognize the signatures of various sages. Rashi explains that דיסקי were letters of responsa, as well as letters of greeting.
This is one example, among several, that show there was a practice of recording Torah well before Rebbe canonized the mishnah. Elsewhere we have seen recordings of berachot, scrolls on which people recorded novellae cited in the beit midrash, and Aramaic translation/commentary in the targumim. The Sfat Emet (Megilah 3a) contends that the prohibition against recording Torah was specifically against publishing it.
The gemara here records Hillel’s justification for formalizing the Prozbul; the issue was a need to ensure a flow of (interest-free) loans. This was critical, since it was (and still is) the greatest form of tzedakah - it allows for a greater magnitude of aid than we could ever see from gifts. Therefore the sages made numerous enactments to encourage lending - this Prozbul, as well as requiring that debts be repaid with a strong currency, eliminating intense interrogation of witnesses and more. This is what the sages called שלא תנעול דלת בפני לווין, to keep the door from being closed before lenders.
Note the basic debate between Rashi and Tosafot as to how Prozbul works.
The gemara here says that Hillel could subvert Shemitah’s release of overdue debts because Shemitah is rabbinic rather than biblical today. This is a problem for the view (see Erchin 31b-32a) that Shemitah remained biblical throughout the second Beit haMikdash, when Hillel lived!
Tosafot here answers that Hillel created the enactment to apply after the destruction of the Beit haMikdash.
Ramban here finds that answer unacceptable, and argues that one must say it was rabbinic during the second Beit haMikdash.
Tosafot ותקון asks why the sages would have enacted a rabbinic memorial to shemitah, but not to Yovel. He answers that the prohibition against farming during Yovel, coming on the heels of Shemitah, would be too great a difficulty to impose rabbinically. Note that Tosafot must follow the system of counting that we use, that does not count Yovel as part of the Shemitah cycle. This is against the view that Yovel is part of the seven-year Shemitah cycle, and so is not always the year following Shemitah.
Rashi יחרם כל רכושו stresses that this co-opting of the property of people who did not return for the second Beit haMikdash was a verdict of the Great Assembly. Perhaps this is lest one consider it a הוראת שעה of a prophet, and therefore invalid as precedent for rabbinic action.
See Tosafot דאלימי on what kind of Beit Din is needed to perform a Prozbul.
I prefer to take שמחין ביסורין as “joyous despite suffering” rather than “joyous in suffering.” But I could be wrong.