Today is Yom Kippur, the last of the ten Days of Awe. The Days of Awe begin with Rosh Hashanah, the Jewish New Year, the day on which judgments are inscribed in to the Book of Life. Yom Kippur is the Day of Atonement and the Day of Judgment, the last chance to repent for the sins of the prior year before the Book of Life is sealed and your judgment is finalized.
In Jewish law there's something called a Neder, which is a vow any Jew can swear, promising to do anything, that thereby becomes a divine law. This is important because it allows you to take a voluntary act of dedication and consecrate it into a commanded act. (In Judaism, fulfilling obligations gives you more points than doing superfluous stuff.)
In practice this can be disastrous. There's a carefully worked out legal framework to make sure the received commandments are not onerous, but you can say anything and make it a Neder. This is dramatized in the Book of Judges, with the story of Jephthah: