Leviticus 5:6-7

6and he must bring his guilt offering to the LORD for the sin he has committed: a female lamb or goat from the flock as a sin offering. And the priest will make atonement for him concerning his sin.

7If, however, he cannot afford a lamb, he may bring to the LORD as restitution for his sin two turtledoves or two young pigeons—one as a sin offering and the other as a burnt offering.