Leviticus 9:7-9

Living Bible

⁷ Moses then told Aaron to proceed to the altar and to offer the sin offering and the burnt offering, making atonement for himself first, and then for the people, as the Lord had commanded. ⁸ So Aaron went up to the altar and killed the calf as a sacrifice for his own sin; ⁹ his sons caught the blood for him, and he dipped his finger in it and smeared it upon the horns of the altar, and poured out the rest at the base of the altar.