Leviticus 9:8, 9, 18

So Aaron came to the altar and slaughtered the calf as a sin offering for himself.

His sons brought the blood to him, and he dipped his finger into the blood and put it on the horns of the altar; the rest of the blood he poured out at the base of the altar.

He slaughtered the ox and the ram as the fellowship offering for the people. His sons handed him the blood, and he splashed it against the sides of the altar.