Leviticus 9:8-10

New Century Version

⁸ So Aaron went to the altar and killed the bull calf as a sin offering for himself. ⁹ Then his sons brought the blood to him, and he dipped his finger in the blood and put it on the corners of the altar. He poured out the rest of the blood at the bottom of the altar. ¹⁰ Aaron took the fat, the kidneys, and the best part of the liver from the sin offering and burned them on the altar, in the way the Lord had commanded Moses.