Leviticus 5:8-10

Amplified Bible

⁸ He shall bring them to the priest, who shall offer first the one for the sin offering, and shall nip its head at the front of its neck, but shall not sever it [completely]. ⁹ He shall also sprinkle some of the blood of the sin offering on the side of the altar, and the rest of the blood shall be drained out at the base of the altar; it is a sin offering. ¹⁰ The second [bird] he shall prepare as a burnt offering, according to the ordinance. So the priest shall make atonement on his behalf for the sin which he has committed, and it will be forgiven him.