2 If a man vows a vow to the Lord, or swears an oath to bind himself by a pledge, he shall not break his word. He shall do according to all that proceeds out of his mouth.

3 "If a woman vows a vow to the Lord and binds herself by a pledge, while within her father's house in her youth, 4 and her father hears of her vow and of her pledge by which she has bound herself and says nothing to her, then all her vows shall stand, and every pledge by which she has bound herself shall stand. 5 But if her father opposes her on the day that he hears of it, no vow of hers, no pledge by which she has bound herself shall stand. And the Lord will forgive her, because her father opposed her. 6 "If she marries a husband, while under her vows or any thoughtless utterance of her lips by which she has bound herself, 7 and her husband hears of it and says nothing to her on the day that he hears, then her vows shall stand, and her pledges by which she has bound herself shall stand. 8 But if, on the day that her husband comes to hear of it, he opposes her, then he makes void her vow that was on her, and the thoughtless utterance of her lips by which she bound herself. And the Lord will forgive her. 9 (But any vow of a widow or of a divorced woman, anything by which she has bound herself, shall stand against her.) 10 And if she vowed in her husband's house or bound herself by a pledge with an oath, 11 and her husband heard of it and said nothing to her and did not oppose her, then all her vows shall stand, and every pledge by which she bound herself shall stand. 12 But if her husband makes them null and void on the day that he hears them, then whatever proceeds out of her lips concerning her vows or concerning her pledge of herself shall not stand. Her husband has made them void, and the Lord will forgive her. 13 Any vow and any binding oath to afflict herself, her husband may establish,[1] or her husband may make void.

Matthew Henry's Commentary on Numbers 30:2-13

Commentary on Numbers 30:1-2

(Read Numbers 30:1-2)

No man can be bound by his own promise to do what he is already, by the Divine precept, forbidden to do. In other matters the command is, that he shall not break his words, through he may change his mind.

Commentary on Numbers 30:3-16

(Read Numbers 30:3-16)

Two cases of vows are determined. The case of a daughter in her father's house. When her vow comes to his knowledge, it is in his power either to confirm it or do it away. The law is plain in the case of a wife. If her husband allows her vow, though only by silence, it stands. If he disallows it, her obligation to her husband takes place of it; for to him she ought to be in subjection, as unto the Lord. The Divine law consults the good order of families. It is fit that every man should bear rule in his own house, and have his wife and children in subjection; rather than that this great rule should be broken, or any encouragement be given to inferior relations to break those bonds asunder, God releases the obligation even of a solemn vow. So much does religion secure the welfare of all societies; and in it the families of the earth have a blessing.