Numbers 30:9

every vow of a widow--In the case of a married woman, who, in the event of a separation from her husband, or of his death, returned, as was not uncommon, to her father's house, a doubt might have been entertained whether she was not, as before, subject to paternal jurisdiction and obliged to act with the paternal consent. The law ordained that the vow was binding if it had been made in her husband's lifetime, and he, on being made aware of it, had not interposed his veto [Num 30:10-11]; as, for instance, she might have vowed, when not a widow, that she would assign a portion of her income to pious and charitable uses, of which she might repent when actually a widow; but by this statute she was required to fulfil the obligation, provided her circumstances enabled her to redeem the pledge. The rules laid down must have been exceedingly useful for the prevention or cancelling of rash vows, as well as for giving a proper sanction to such as were legitimate in their nature, and made in a devout, reflecting spirit. Next: Numbers Chapter 31

— Jamieson-Fausset-Brown Commentary (public domain)