Leviticus 5:4 - Joseph Benson’s Commentary on the Old and New Testaments

If a soul swear Rashly and unadvisedly, without consideration, either of God's law or of his own power or right, as David did, 1 Samuel 25:22: so the following word, לבשׂא, lebattee, rendered pronouncing, properly signifies, Psalms 106:33. The meaning is, Whosoever shall, in a passion or otherwise, make an oath to do a person an injury, or to do him a kindness, and afterward, forgetting his oath, shall fail in the performance, so soon as he recollects himself he shall make atonement for his offence. In the case of threatening private revenge, or to do evil in any other way, the oath ought to be recalled, as being a thing in itself unlawful. But the person who thus rashly uttered that oath was involved in guilt, and needed to have his sin expiated. And for a similar reason he was punishable, if with an oath he promised to do any thing that was not in his power. It may also be understood of a person's making a vow to do something either beneficial or hurtful to himself, as to fast, or afflict himself. For that is the sense of swearing to do evil, or to his own hurt. And it be hid from him That is, if through forgetfulness he neglect punctually to perform what he promised on oath. When he knoweth it, he shall be guilty in one of these As soon as he recollects himself, and comes to the knowledge of such an omission, he shall be obliged to expiate his offence by sacrifices, being guilty in one of these; that is, in one of the things which are forbidden to be done.