And Aaron shall bring the bullock of the sin offering, which is for himself, and shall make an atonement for himself, and for his house, and shall kill the bullock of the sin offering which is for himself: (Leviticus 16:11)
This bullock had been presented to the Lord (v. 6); now it was brought forward for sacrifice. Before Aaron was prepared to make atonement for others, he must make an atonement for himself.