Leviticus 5:4-5

5:4 or when a person swears an oath, speaking thoughtlessly with his lips, whether to do evil or to do good, with regard to anything which the individual might speak thoughtlessly in an oath, even if he did not realize it, but he himself has later come to know it and is guilty with regard to one of these oaths – 5:5 when an individual becomes guilty with regard to one of these things he must confess how he has sinned,