Leviticus 5:3-7

Or if he touches human uncleanness, of whatever sort his uncleanness may be with which he becomes unclean, and it is hidden from him, and then he comes to know it, he will be guilty.

Or if a person swears thoughtlessly with his lips to do evil or to do good, in whatever matter people speak thoughtlessly with an oath, and it is hidden from him, and then he comes to know it, he will be guilty of one of these things.

So it shall be when he becomes guilty of one of these things, that he shall confess that in which he has sinned.

He shall also bring his guilt offering to the Lord for his sin which he has committed, a female from the flock, a lamb or a goat as a sin offering. So the priest shall make atonement on his behalf for his sin.

‘But if he 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 doves, one as a sin offering and the other as a burnt offering.