What is the ruling on a vow (Nadr) conditional on a future event, such as 'Upon me is fasting one day, if so-and-so arrives forever'?
General Chapter
Al-Mughni
Book of Vows
Primary text
Such a vow obligates the fast for the time following the fulfillment of the condition in the future. The specific day upon which the condition is met is excluded from the vow. A fast vowed conditionally does not include the days of Ramadan because Ramadan cannot be separated from its days, and fasting those days for the vow instead of for Ramadan is impermissible.
Supporting text
According to the view attributed to Al-Kharqi, the day of arrival in Ramadan does enter into the vow, and the fast suffices for both Ramadan and the vow.