Leviticus 5:3-5

3Or if he touches human uncleanness—whatever kind it may be—and he becomes unclean, but he is unaware of it, when he recognizes it, he will be guilty.

4Or if anyone swears [an oath] thoughtlessly or impulsively aloud that he will do either evil or good, in whatever manner a person may speak thoughtlessly or impulsively with an oath, but he is unaware of it, when he recognizes it, he will be guilty in one of these.

5So it shall be when a person is guilty in one of these, that he shall confess the sin he has committed.