Leviticus 9:8-10

So Aaron came near to the altar and put to death the ox for the sin-offering for himself; And the sons of Aaron gave him the blood and he put his finger in the blood and put it on the horns of the altar, draining out the blood at the base of the altar; But the fat and the kidneys and the fat on the liver of the sin-offering were burned by him on the altar as the Lord gave orders to Moses.