If someone vows to fast a particular day every year for as long as he lives, the vow is binding; yet whenever that day coincides with Ramadan or with any of the days on which fasting is forbidden, he is not required to make it up. Although the jurists differ greatly on this question, the opinion I have just reported is, in my judgment, the correct one.

Mālik permitted a person who had vowed to fast the third of the days of tashrīq (the thirteenth of Dhūl-Ḥijjah), or a certain day in Dhūl-Ḥijjah, or who had taken upon himself the fast of ʿĀshūrāʾ, to fast that day when it arrives and even to use it as the first day of a series of consecutive fasts. According to Mālik, however, that day may not be used to make up a missed fast of Ramadan, nor may it be observed as a voluntary fast.

The other scholars of Medina, and many beyond them, categorically forbade fasting on that day in any circumstance, relying on the Prophet’s—peace and blessings be upon him—prohibition of fasting on the days spent at Minā; he made no distinction between the first of those days and the last.

Whoever vows to fast a day without specifying which one—such as a man who says that a single day of fasting is due from him—and then fails to fast it, whether excusably or not, must make it up. The same applies to a woman: she must make up whatever of that vowed day coincides with her menstrual period.

If a person vows to fast a particular day but falls ill on that day, nothing is required of him unless he had intended to make it up; should he then neglect the makeup, it becomes obligatory. The same ruling applies to a woman who vows to fast a specific day for as long as she lives but then falls ill or menstruates on that day: she is not required to make up what she missed on account of illness or menses unless she had already intended to do so. Some have said that she must make it up unless she had expressly intended otherwise, but the first opinion is the sounder one, God willing.