Leviticus 9:7-10

Then Moses said to Aaron, “Come to the altar and sacrifice your sin offering and your burnt offering to purify yourself and the people. Then present the offerings of the people to purify them, making them right with the LORD, just as he has commanded.” So Aaron went to the altar and slaughtered the calf as a sin offering for himself. His sons brought him the blood, and he dipped his finger in it and put it on the horns of the altar. He poured out the rest of the blood at the base of the altar. Then he burned on the altar the fat, the kidneys, and the long lobe of the liver from the sin offering, just as the LORD had commanded Moses.