Leviticus 5:9-11

Amplified Bible

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.

¹¹ ‘But if he cannot afford to bring two turtledoves or two young pigeons, then he shall bring as his offering for his sin the tenth part of an ^[a]ephah of fine flour as a sin offering; he shall not put [olive] oil or incense on it, for it is a sin offering.