John Wesley on Numbers 30:13

To afflict her soul - Herself by fasting, by watching, or the like. And these words are added to shew that the husband had this power not only in those vows which concerned himself or his estate, but also in those which might seem only to concern her own person, or body, and the reason is, because the wife's person or body being the husband's right; she might not do any thing to the injury of her body without his consent.