Leviticus 4:17, 18, 25

He shall dip his finger into the blood and sprinkle it before the LORD seven times in front of the curtain.

He is to put some of the blood on the horns of the altar that is before the LORD in the tent of meeting. The rest of the blood he shall pour out at the base of the altar of burnt offering at the entrance to the tent of meeting.

Then the priest shall take some of the blood of the sin offering with his finger and put it on the horns of the altar of burnt offering and pour out the rest of the blood at the base of the altar.