Leviticus 5:10, 12, 18

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.

He shall bring it to the priest, who shall take a handful of it as a memorial portion and offer it up in smoke on the altar, with the offerings by fire to the LORD; it is a sin offering.

He is then to bring to the priest a ram without blemish from the flock, according to your valuation, for a guilt offering. In this way the priest shall make atonement for him regarding the error which he committed unintentionally and did not know it, and he shall be forgiven.