Leviticus 5:4-6

Or if any one swear rashly with his lips to do evil, or to do good, whatsoever it be that a man shall utter rashly with an oath, and it be hid from him; when he knoweth of it, then he shall be guilty in one of these things. And it shall be, when he shall be guilty in one of these things, that he shall confess that wherein he hath sinned: and he shall bring his trespass-offering unto Jehovah for his sin which he hath sinned, a female from the flock, a lamb or a goat, for a sin-offering; and the priest shall make atonement for him as concerning his sin.