مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٥٦٤ - Vow and Covenant

vow to give alms, or to fast on the firstof the month, or to offer prayers of the first of the month, and performs these acts before that day or after it, it does not suffice. Moreover, if he makes a vow that hewill give alms when his patient recovers, but gives alms before the recovery of the patient it does not suffice.
٢٦٦١. If a person makes a vow that he will fast but does not specify the time and number of fast it is sufficient if he observes fast on one day. And if he makes avow that he will offer prayers but does not specify its quantity and particulars, it is sufficient if he offers one two rakat prayers. And if he makes a vow that he willgive alms, but does not specify its quality or quantity and he gives something about which it may be said that he has given alms he has performed his vow. And if he makes avow that he will do something to please the Almighty Allah he fulfil his vow, if he offers one prayers, or observes one fast, or gives away something by way of alms.
٢٦٦٢. If a person makes a vow that he will observe fast on a particular day, he should observe fast on that very day; and in case he does not observe fast on thatday intentionally he should, besides observing the lapsed fast of that day, also make atonement for it. And what is more apparent is that its atonement is the same as it isfor violating the oath, as will be told later. However, he has the option to proceed on a journey on that day and do without observing fast, and in case he is journeying itis not necessary for him to make an intention of staying for ten days and observe fast. And in case he does not fast on account of travelling or because of some other excuse,like ailment (or menses in the care of women) it is necessary for him to observe the lapsed fast of that day.
٢٦٦٣. If a person intentionally violates his vow he should make an atonement for it.
٢٦٦٤. If a person makes a vow to abandon an act till a