Leviticus 5:6-7

6Then you must bring to the Lord as the penalty for your sin a female from the flock, either a sheep or a goat. This is a sin offering with which the priest will purify you from your sin, making you right with the Lord.

7“But if you cannot afford to bring a sheep, you may bring to the Lord two turtledoves or two young pigeons as the penalty for your sin. One of the birds will be for a sin offering, and the other for a burnt offering.