Ellicott's Commentary for English Readers
(2) If a man vow a vow unto the Lord . . . —Two kinds of vows are spoken of in this verse—viz., the neder, which is here rendered vow, and which denotes primarily a positive vow, or vow of performance, and the issar, which is here rendered bond, and which denotes a negative vow, or a vow of abstinence. It is natural to suppose that at the expiration of the protracted wanderings in the wilderness the pious Israelites would be desirous of testifying their gratitude by dedicating themselves, or some portion of their substance beyond that which the law demanded, to the service of the Lord. And hence, although some regulations respecting vows had already been made (see Leviticus 27), it was needful that before their entrance into the land of Canaan some additions should be made to the law which pertained to the nature and obligation of vows.
He shall not break his word . . . —The sacred character of a vow is enforced in these words; and a timely caution was thus given to the Israelites that it was better for them not to vow than to vow and not to pay. (Comp. Ecclesiastes 5:2-5.)
And Moses spake unto the heads of the tribes concerning the children of Israel, saying, This is the thing which the LORD hath commanded.
If a woman also vow a vow unto the LORD, and bind herself by a bond, being in her father's house in her youth;(3) If a woman also . . . —Four distinct cases are contemplated in the following verses in regard to vows taken by women:—(1) that of an unmarried woman, living, in her youth, in the house of her father; (2) that of a woman who is unmarried at the time of making a vow, but enters into the state of marriage before the vow is fulfilled; (3) that of a widow, or of a divorced woman; and (4) that of a married woman. The sanctity and obligations of the fifth commandment are distinctly recognised and enforced in these verses. (See Matthew 15:4-5.) Whenever the vow which the young daughter had made should come to the ears of her father, he had the power either to ratify or to disannul it. If he remained silent the vow was ratified; if he disallowed the vow, the obligation to fulfil it no longer remained in force.
But if her father disallow her in the day that he heareth; not any of her vows, or of her bonds wherewith she hath bound her soul, shall stand: and the LORD shall forgive her, because her father disallowed her.(5) The Lord shall forgive her—i.e., she would not incur the guilt or punishment which would otherwise have been incurred by neglecting to fulfil the vow which she had made.
And if she had at all an husband, when she vowed, or uttered ought out of her lips, wherewith she bound her soul;(6) And if she had at all an husband . . . . —Better, And if she should be married to a husband whilst her vows are upon her, or the rash utterance of her lips wherewith she hath bound her soul. The case here contemplated appears to be that of a woman who married whilst under a vow. On the other hand the case of a woman who takes a vow after marriage is treated of further on in Numbers 30:10-13. The cognate verb of the word mibta, rash utterance, occurs in Leviticus 5:4, and seems to denote something which is uttered without reflection.
And if she vowed in her husband's house, or bound her soul by a bond with an oath;(10) And if she vowed in her husband’s house, or bound her soul . . . —i.e., if she took a vow of performance or of abstinence whilst in the house of her husband.
Every vow, and every binding oath to afflict the soul, her husband may establish it, or her husband may make it void.(13) Every vow, and every binding oath to afflict the soul.—Reference is again made to the two kinds of vows which are treated of in this chapter—viz., a vow to do anything, and a vow to abstain from anything.