John Gill Commentary Leviticus 4:18

"And he shall put of the blood upon the horns of the altar which is before Jehovah, that is in the tent of meeting; and all the blood shall he pour out at the base of the altar of burnt-offering, which is at the door of the tent of meeting." — Leviticus 4:18 (ASV)

(See Gill on Leviticus 4:16).