According to the Bible, a man must fulfil any vows he might make to God. He must not break his word. On the other hand, a woman's vow is not necessarily binding on her. It has to be approved by her father, if she is living in his house, or by her husband, if she is married. If a father/husband does not endorse his daughter's/wife's vows, all pledges made by her become null and void:
"But if her father forbids her when he hears about it, none of her vows or the pledges by which she obligated herself will stand ... Her husband may confirm or nullify any vow she makes or any sworn pledge to deny herself." [Num. 30:2-15]
Why is it that a woman's word is not binding per se? The answer is simple: because she is owned by her father, before marriage, or by her husband after marriage. The father's control over his daughter was absolute to the extent that, should he wish, he could sell her! It is indicated in the writings of the Rabbis that:
"The man may sell his daughter, but the woman may not sell her daughter; the man may betroth his daughter, but the woman may not betroth her daughter." [Swidler, op. cit., p. 141]
The Rabbinic literature also indicates that marriage represents the transfer of control from the father to the husband: "betrothal, making a woman the sacrosanct possession - the inviolable property - of the husband ... " Obviously, if the woman is considered to be the property of someone else, she cannot make any pledges that her owner does not approve of.
It is of interest to note that this Biblical instruction concerning women's vows has had negative repercussions on Judaeo-Christian women till early in this century. A married woman in the Western world had no legal status. No act of hers was of any legal value. Her husband could repudiate any contract, bargain, or deal she had made. Women in the West (the largest heir of the Judaeo-Christian legacy) were held unable to make a binding contract because they were practically owned by someone else. Western women had suffered for almost two thousand years because of the Biblical attitude towards women's position vis-à-vis their fathers and husbands. [Matilda J. Gage, Woman, Church, and State, New York: Truth Seeker Company, 1893, p. 141]
In Islam, the vow of every Muslim, male or female, is binding on him/her. No one has the power to repudiate the pledges of anyone else. Failure to keep a solemn oath, made by a man or a woman, has to be expiated as indicated in the Qur'an:
"He [God] will call you to account for your deliberate oaths: for expiation, feed ten indigent persons, on a scale of the average for the food of your families; Or clothe them; or give a slave his freedom. If that is beyond your means, fast for three days. That is the expiation for the oaths you have sworn. But keep your oaths." [Al-Qur'an 5:89]
Companions of the Prophet Muhammad, men and women, used to present their oath of allegiance to him personally. Women, as well as men, would independently come to him and pledge their oaths:
"O Prophet, When believing women come to you to make a covenant with you that they will not associate in worship anything with God, nor steal, nor fornicate, nor kill their own children, nor slander anyone, nor disobey you in any just matter, then make a covenant with them and pray to God for the forgiveness of their sins. Indeed God is Forgiving and most Merciful." [Al-Qur'an 60:12]
A man could not swear the oath on behalf of his daughter or his wife. Nor could a man repudiate the oath made by any of his female relatives.