“...the miser” indicates that the disapproval or prohibition applies specifically to a conditional, reciprocal vow, not to a vow undertaken voluntarily as an act of devotion. The latter is a pure act of drawing near to Allah, for the person making it has a sound purpose: that he may be rewarded for it with the reward of a duty, which is greater than the reward for a voluntary act. This is the vow intended—Allah knows best—by His saying: “They fulfil their vows,” rather than the former type.
Al-Hafiz said in al-Fath (11/500):
“Al-Tabari transmitted through an authentic chain from Qatadah regarding Allah’s saying, ‘They fulfil their vows.’ He said: They would vow acts of obedience to Allah, such as prayer, fasting, zakah, Hajj, and ‘umrah, as well as what had been made obligatory for them; so Allah called them righteous. This explicitly shows that the praise concerns a vow other than a conditional vow.”
Earlier, he said: “Al-Qurtubi stated decisively in al-Mufhim that the prohibitions reported in the hadiths refer to conditional vows. He said:
The prohibition applies, for example, when someone says: ‘If Allah cures my sick person, then I shall give such-and-such charity.’
The reason for its disapproval is that, by making the performance of the stated act of devotion dependent upon the fulfilment of that purpose, it becomes apparent that what he did was not motivated by a pure intention to draw near to Allah. Rather, he treated it as a transaction. This is further clarified by the fact that, if his sick person were not cured, he would not give the charity that he had made conditional upon his recovery. This is the state of the miser, for he does not part with anything of his wealth except in return for an immediate compensation that will generally exceed what he has given. This is the meaning indicated in the hadith by the words: ‘It merely draws out from the miser what the miser would not otherwise give.’
An ignorant person may also hold the belief that a vow necessitates the attainment of that purpose, or that Allah grants him that purpose on account of the vow. Both are alluded to in the other words of the hadith: ‘For a vow repels nothing of Allah’s decree.’ The first state borders on disbelief, and the second is a clear error.”
Al-Hafiz said: