Prayer may be obligatory or voluntary. Thus, if he says, “I vow to Allah that I will perform the Zuhr prayer,” it becomes binding upon him on two grounds: its being obligatory by the original ruling of the Sacred Law, and its being obligatory by virtue of the vow. Likewise, if he says, “I vow to Allah that I will pay the zakah on my wealth,” it becomes binding upon him on two grounds: the Sacred Law and the vow. If he does not pay the zakah, he must offer the expiation for an oath, in addition to being sinful. Had he not made the vow, the expiation for an oath would not have been due from him, though he would still be sinful for neglecting the zakah. This is the benefit of saying that a vow may pertain to an obligatory act. This is not merely redundant; although, with respect to prayer, it may be said that this does not present an issue for us, since abandoning it constitutes disbelief.
What matters is that a vow concerning an obligatory act is valid.
His statement, “whether unconditional”: an unconditional vow is like saying, “I vow to Allah that I will pray two rak'ahs,” or, “I vow to Allah that I will recite one juz' of the Quran.”
His statement, “or conditional”: the author illustrated this by saying:
“Such as his saying, ‘If Allah cures my sick person’”—meaning: if Allah cures my sick person, then I vow to Allah that I will give one hundred riyals in charity. Whenever the sick person is cured, this becomes binding upon him. If the person dies, nothing becomes binding upon him; likewise, if he remains ill, nothing becomes binding upon him. If he is cured after the one who made the vow has died, nothing is due from him, because the condition did not occur during his lifetime, and the basic principle is that one is free of liability.
But if he is cured while the person who made the vow is insane—may Allah grant us well-being—is anything binding upon him or not? We have a cause and a condition: the cause for the obligation to give these dirhams in charity is the vow, while the condition for the obligation is recovery. The cause of obligation arose from the person while he was legally accountable, whereas the condition of obligation arose while he was not legally accountable; yet he is liable for financial obligations,