For this reason the Prophet (peace and blessings be upon him) forbade making vows, saying, “It brings no good; it only wrings charity from a miser.” If, however, a person has already made a vow, such vows fall into three categories: one whose ruling is that of an oath, a second that is a vow of disobedience, and a third that is a vow of obedience.

1. A vow that takes the ruling of an oath: This is when a person means by it nothing more than to stress or emphasize a statement—whether in negation, affirmation, verification, or encouragement. For example, someone is told, “You have informed us of such-and-such, but we do not believe you,” and he replies, “If I am lying, I vow to Allah that I shall fast for a whole year.” Clearly his purpose is to reinforce his statement so that people will believe him; therefore it is treated as an oath, for he intended to confirm what he said. The same applies when the aim is motivation, as when one says, “If I do not do such-and-such, then I vow to Allah that I will fast for a year.” Here too the intention is to spur oneself on to perform the stated act, and its ruling is likewise that of an oath. The evidence is the Prophet’s saying, “Actions are only by intentions, and each person shall have only what he intended.” Since he intended an oath, he is judged according to that intention.

2. The second category is the prohibited vow. If a person makes such a vow, it is unlawful for him to fulfill it. An example is someone saying, “I vow to Allah that I will drink wine.” This is an unlawful vow, so it is impermissible for him to drink wine; instead, he must offer the expiation for breaking an oath, according to the stronger opinion.