Leviticus 16:18-19

18“Then he shall come out to the altar that is before the LORD and make atonement for it. He shall take some of the bull’s blood and some of the goat’s blood and put it on all the horns of the altar.

19He shall sprinkle some of the blood on it with his finger seven times to cleanse it and to consecrate it from the uncleanness of the Israelites.