Leviticus 16:14-15

14And he is to take some of the bull’s blood and sprinkle it with his finger on the east side of the mercy seat; then he shall sprinkle some of it with his finger seven times before the mercy seat.

15Aaron shall then slaughter the goat for the sin offering for the people and bring its blood behind the veil, and with its blood he must do as he did with the bull’s blood: He is to sprinkle it against the mercy seat and in front of it.