Albert Barnes Commentary Numbers 30:6

"And if she be [married] to a husband, while her vows are upon her, or the rash utterance of her lips, wherewith she hath bound her soul," — Numbers 30:6 (ASV)

Rather, And if she shall at all be a husband’s, and her vows shall be upon her, or a rash utterance of her lips, with which she has bound her soul, etc. The phrase “at all” suggests that the case of a girl betrothed but not yet actually married is especially considered here. After betrothal, a woman continued to reside in her father’s house until her marriage; but her property was from that time on vested in her husband, and she was regarded as personally his to such a degree that an act of faithlessness to him was, like adultery, punishable with death (Deuteronomy 22:23–24). Therefore, he had the right to control her vows even before he actually took her home as his wife.