Leviticus 5:4-10

4Or if a person 1swears thoughtlessly with his lips to do evil or to do good, in whatever matter a man may speak thoughtlessly with an oath, and it is hidden from him, and then he comes to know it, he will be guilty in one of these. 5So it shall be when he becomes guilty in one of these, that he shall 2confess that in which he has sinned. 6He shall also bring his guilt offering to the Lord for his sin which he has 3committed, 4a female from the flock, a lamb or a 5goat as a sin offering. So the priest shall make atonement on his behalf for his sin.

7‘But if 6he cannot afford a lamb, then he shall bring to the Lord his guilt offering for that in which he has sinned, two turtledoves or two young pigeons, 7one for a sin offering and the other for a burnt offering. 8He shall bring them to the priest, who shall offer first that which is for the sin offering and shall nip its head at the front of its neck, but he 8shall not sever it. 9He shall also sprinkle some of the blood of the sin offering 9on the side of the altar, while the rest of the blood shall be drained out 10at the base of the altar: it is a sin offering. 10The second he shall then prepare as a burnt offering 11according to the ordinance. 12So the priest shall make atonement on his behalf for his sin which he has 13committed, and it will be forgiven him.