In the synagogue the Torah is read aloud in a fixed annual cycle of fifty-four weekly portions (parashiyot), one each Shabbat morning, with certain adjacent portions doubled in ordinary years so the sequence fits the calendar. Each portion is named for a distinctive word near its opening and is paired with a haftarah, a reading from the Prophets. The cycle closes and restarts on Simchat Torah. Achrei Mot ('After the Death', Leviticus 16:1-18:30) prescribes the service of Yom Kippur, the high priest's entry into the Holy of Holies and the sending of the scapegoat to Azazel, together with the prohibition of consuming blood and a list of forbidden sexual relations. The chapter on the Yom Kippur rite is read on that day.
The Yom Kippur service prescribed in Achrei Mot, the high priest's sole annual entry into the Holy of Holies, wearing plain white linen rather than his usual ornamented garments, and the casting of lots over two goats, one sacrificed, one sent into the wilderness bearing the people's sins to Azazel (Leviticus 16:8-10, 16:21-22), is read by the classical commentary tradition as the most solemn and dangerous rite in the entire priestly calendar, later Mishnaic tractate Yoma describing elaborate precautions taken to ensure the high priest survived the entry. The identity and meaning of Azazel, to whom the second goat is dispatched, has been debated since antiquity, ancient sources including some strands of Second Temple literature reading it as a wilderness demon, classical rabbinic commentary more often reading it simply as a rugged, precipitous place.