Nedarim 76: Defining a Day
More on the question of whether one can nullify vows in advance. With a parallel to the impurity and purity of seeds. Also, a new mishnah, on the "day" that the vow can be revoked. Plus, the Gemara on how to define the day - is it 24 hours or specifically the calendar date that the vow is made.
The skinny
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