Leviticus 5:1, 4

‘If anyone sins after he hears a public adjuration (solemn command to testify) when he is a witness, whether he has seen or [otherwise] known [something]—if he fails to report it, then he will bear his guilt and be held responsible.

Or 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. [Mark 6:23]