“A man who makes a vow…” (Bamidbar 30:3)
It is a positive commandment that we must deal with a person who makes a vow in the way that the Torah prescribes. This means to say that there is no obligation to repeal the vow, but we must follow these laws in the way that is explicit in the relevant verses of the Torah. It is explicit in the verses that the husband can annul the vows of his wife and that a father can annul the vows of his daughter, and Chazal have a transmission that even a wise man can repeal a vow. It follows that when a wise man repeals a vow in the way that the Torah prescribes, he has fulfilled this commandment, whereas if he does not do it in the prescribed manner, (e.g. the man who repeals the vow is not an expert,) then not only has the vow not been repealed, but he has also transgressed this commandment.
Amongst the roots of this subject are that making a vow is like creating a prohibition on something which is essentially permitted, and it is like saying “This permitted object should be forbidden to me just like an offering which Hashem forbade.” In this way we have the power to forbid that which is permitted, as the Torah says “To make a prohibition on himself, he may not break his word!”.
This commandment applies in all places and at all times, to men but not to women, as only men can repeal vows. One who repeals a vow unlawfully, even though his repealing does not take effect, has transgressed this commandment.