Leviticus 9:5-9

And they brought that which Moses commanded before the tabernacle of the congregation: and all the congregation drew near and stood before the LORD.

And Moses said, This is the thing which the LORD commanded that ye should do: and the glory of the LORD shall appear unto you.

And Moses said unto Aaron, Go unto the altar, and offer thy sin offering, and thy burnt offering, and make an atonement for thyself, and for the people: and offer the offering of the people, and make an atonement for them; as the LORD commanded.

Aaron therefore went unto the altar, and slew the calf of the sin offering, which was for himself.

And the sons of Aaron brought the blood unto him: and he dipped his finger in the blood, and put it upon the horns of the altar, and poured out the blood at the bottom of the altar: