Vows Are to Be Kept (Numbers 30)
Vows and sworn oaths were not to be entered into lightly. They were to be kept. But there were certain circumstances in which they could be overruled. In ancient Israel, an unmarried woman was under the protection and supervision of her father. If she entered into some agreement or vow, this might have put her father, the one responsible for her, under an obligation that he was either unable or unwilling to fulfill. So it was up to him whether or not to overrule her or allow her vow to stand. The same law applied to married women, except that the one who decided whether or not to allow the agreement to stand was, of course, the husband. If the wife was already bound by some prior vow at the time of marriage, her new husband had the opportunity to overrule it as soon as he became aware of it. But if he let it stand beyond that, it would remain in force. In the case of a widow or divorced woman, her vow would automatically stand as it could not obligate a husband or father.
In the New Testament dispensation we make a vow or covenant with Christ. The Father calls and grants us repentance and faith. We agree to bury the old man of sin. God gives us His Spirit and we are no longer our own. Ours is an eternal vow or covenant. And, just as in the Old Testament, it is not to be entered into by the immature. Just the same, marriage is a solemn vow made to God and spouse. But as for swearing oaths in general, Christ has instructed that we not do so (Matthew 5:33-37). Rather, just giving our word should be enough and should serve just as well.