Chapter on Vows
(1) A vow is valid when made by any legally accountable person, even by a non-Muslim. If someone merely says, “I owe Allah a vow,” or similar words, what becomes binding on him is the expiation for an oath.
A vow uttered out of obstinacy or anger gives its maker the choice between fulfilling the vow or paying the expiation for an oath; the same ruling applies to a vow concerning something that is merely permissible.
For a vow to do something disliked—such as divorcing—it is recommended that he offer the expiation and not carry the act out.
A vow to commit a sin—such as killing or drinking wine—must not be fulfilled; rather, he must offer the expiation.
A devotional vow—like undertaking prayer, fasting, pilgrimage, and the like—must be fulfilled. Included in this category is the conditional statement: “If Allah heals my sick one, or safeguards my property, and the like, then I owe Allah such-and-such,” once the condition is met.
Whoever vows to give all of his wealth in charity fulfills the vow by giving one third of it.
If a person vows to fast a month or the like, he is required to fast the days consecutively, not as scattered days, unless he expressly stipulated (2) or intended otherwise.