Nedarim 65: Nebuchadnezzar's Knowledge of Halakhah

Dissolving a vow that pertains to another person can only be done in the presence of that other person. With a proof from Moses and Jethro - and Midian and Egypt. Plus, a story about Nebuchadnezzar and his shame before Tzidkiyahu. Also, 3 mishnayot: openings to annul a vow, beginning with new developments. For example, a vow to keep out if certain property because of a dog or a snake, with the subsequent discovery that the dog/snake died, and the vow is no longer relevant. Plus, an opening to dissolve a vow because if the injunctions in the Torah against bearing a grudge (if the vow is rooted in a grudge). Also, the case of a man vowing that his wife won't benefit from him without realizing he'd need to pay her ketubah - and then be left with nothing. Had he but known, he wouldn't have made such a vow, of course.