Leviticus 9:4-8

Also a bullock and a ram for peace offerings, to sacrifice before the LORD; and a meat offering mingled with oil: for to day the LORD will appear unto you.

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.