Thus, if a woman vows to fast on the day of her menstruation, we say: “Do not fast; you must offer the expiation for an oath.” Must she make it up? No, she need not make it up, because the prohibition is due to a factor connected to the person herself, and thus no make-up is required of her.
But if she vows to fast on the day of Eid, she must not fast—not because of any factor connected to herself, but because of a factor connected to the time.
The same applies to place: if a person vows to pray in a graveyard, we say, “Do not pray, for this is unlawful.” But must he make it up or not? There is a difference of opinion. According to the school, he must make it up and offer the expiation for an oath, because the factor involved is connected to the place.
The stronger view is that he need not make it up, whether the factor is connected to the time, the place, or the person; rather, he must offer the expiation for an oath, because the basic principle is that this vow was not binding in the first place.
The fifth type is a vow of righteousness, whether unconditional or conditional, such as vowing to perform prayer, fast, pilgrimage, and the like—for example, saying, “If Allah cures my sick person or brings my absent property safely back to me, then I owe Allah such-and-such.” If the condition is fulfilled, he must fulfill the vow, except when he vows to give all his wealth in charity, or a specified amount of it exceeding one-third of the total; in that case, giving one-third suffices for him.
His statement: “The fifth type is a vow of righteousness, whether unconditional or conditional.” Righteousness means performing a virtuous deed, just as voluntary worship means performing an act of obedience, and devotional practice means performing a rite of worship. Thus, a vow of righteousness has the same meaning as what we call a vow of obedience, because obedience is righteousness.
His statement: “Such as vowing to perform prayer, fast, pilgrimage, and the like”—such as charity, the lesser pilgrimage, visiting the sick, following funeral processions, and similar acts. A vow of obedience must be fulfilled, due to the Prophet’s statement, peace and blessings be upon him: “Whoever vows to obey Allah must obey Him.” (1)
The apparent meaning of the author’s words is that this includes both obligatory and non-obligatory acts.