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; In her youth - That is, say the rabbins, under twelve years of age; and under thirteen in case of a young man. Young persons of this age were considered to be under the authority of their parents, and had consequently no power to vow away the property of another. A married woman was in the same circumstances, because she was under the authority of her husband. If however the parents or the husband heard of the vow, and objected to it in the same day in which they heard of it, (Numbers 30:5), then the vow was annulled; or, if having heard of it, they held their peace, this was considered a ratification of the vow.
A rash vow was never to be kept; "for," says Philo, and common sense and justice say the same, "he who commits an unjust action because of his vow adds one crime to another,
1. By making an unlawful vow;
2. By doing an unlawful action."