When Yom Kippur falls on a Shabbat, there is a special reading: Chapter 16 of Leviticus. In it are described the special sacrifices to be performed: a bull and a hairy goat. There is a description of how this is to be done. Aaron is to take a live hairy goat, confess all the sins of the Children of Israel whele he leans two hands on the goat’s head, then have it sent out into the wilderness, bearing upon itself all the iniquities.
Aaron washes all his clothing and himself then makes these sacrifices on behalf of the people.