Yom Kippur in Early Judaism

In biblical literature, the Day of Atonement figures only in the priestly calendars and in the priestly narrative in Leviticus 16. It is quintessentially a Temple-based observance: the annual day on which the sanctuary is to be purged of the accumulated sins and impurities of the people, in an almost physical sense. Outside the Temple, it is marked by fasting and other forms of self-abnegation in recognition of the gravity of the occasion. This is also how the day is portrayed in Second Temple–period and rabbinic literature. The Mishnah and Tosefta detail at length the preparations for, and conduct of, the ritual by the high priest in the Temple, perhaps reflecting a nostalgic attempt to preserve the lost Temple rites imaginatively. Rabbinic literature also focuses on the details of fasting and the importance of repentance and confession on the Day of Atonement.