Is fulfilling a vow involving prayer in the Prophet's Mosque or Al-Aqsa Mosque obligatory?
General Chapter
Al-Mughni
Book of Vows
Primary text
Fulfilling a vow to pray in the Prophet's Mosque or Al-Aqsa Mosque is obligatory. This is supported by the narration where 'Umar vowed to perform I'tikaf (seclusion) for one night in Al-Masjid al-Haram, and the Messenger of Allah, peace be upon him, commanded him to fulfill his vow. The obligation exists because prayer in these mosques carries immense virtue; the Prophet, peace be upon him, stated that a prayer in his mosque is better than a thousand prayers elsewhere, except Al-Masjid al-Haram, and a prayer in Al-Masjid al-Haram is equivalent to one hundred thousand prayers. If it is a virtue and an act of obedience, it becomes binding upon being vowed, just like vowing to prolong recitation.
Supporting text
The argument that acts without a basis in the law are not binding by vow is refuted by the validity of vowing to perform Umrah, which becomes binding upon the vow even though it is not universally obligatory according to that school of thought.