Issue 2658...
Issue 2658: If a person makes a vow that he will perform or abandon a normal act, the performing or abandoning of which has equal merits, his vow is not in order. But if performing it is better in some respect, and a person makes a vow keeping that merit in view, for example, if he makes a vow that he will eat a certain food so as to gain strength for worshipping Allah, his vow will be in order.
Also, if its renouncing is better in some respect, and the vow to renounce it is made with that intention, for example, if he finds smoking is harmful and makes a vow not to smoke, his vow is in order. However, at any time when he feels that smoking is not harmful for him, the vow will cancel by itself.
Issue 2659: * If a person makes a vow, that he will offer his obligatory prayers at a place where offering does not inherently carry higher spiritual merits, for example, he makes a vow to offer his prayers in a certain room, his vow will be valid, only if, offering prayers there has some merit, like, being able to concentrate better due to solitude. Issue 2660: If a person makes a vow to perform an act, he should perform it in strict accordance with his vow.
If he makes a vow to give Sadaqa, or to fast on the first day of every month, or to offer prayers of the first of the month, if he performs these acts before that day or after, it will not suffice. Also, if he makes a vow that he will give Sadaqa when a patient recovers, but gives away before the recovery of the patient, it will not suffice. Issue 2661: If a person makes a vow that he will fast, without specifying the time and the number of fasts, it will be sufficient if he observes one fast.
And if he makes a vow that he will offer prayers, but does not specify its number and particulars, it will be sufficient if he offers a two rak'at prayers. And if he makes a vow that he will give Sadaqa, not specifying its nature or quantity, and he gives something which can be deemed as Sadaqa, his vow will be fulfilled.
And if he simply makes a vow that he will act to please Almighty Allah, his vow will be fulfilled if he offers one prayers, or observes one fast, or gives away something by way of Sadaqa. Issue 2662: * If a person makes a vow that he will observe fast on a particular day, he should observe fast on that very day; and if he does not observe fast on that day intentionally, he should, besides observing the qadha for that fast, also give Kaffarah for it.