Leviticus 16:18-19

16:18 “Then he is to go out to the altar which is before the Lord and make atonement for it. He is to take some of the blood of the bull and some of the blood of the goat, and put it all around on the horns of the altar. 16:19 Then he is to sprinkle on it some of the blood with his finger seven times, and cleanse and consecrate it from the impurities of the Israelites.