Answer:
(Fatwa: 1097/1028=B)
According to you, if the mosque will go to the Christian wife after the death of the Arab Muslim, then if she will allow Muslims to pray there they can pray. And this mosque will become waqf and a legal mosque by allowing. If a non-Muslim gives any property in waqf (endowment) considering it an act of virtue this will be accepted in Islam.
If the Arab has built the mosque and allowed common Muslims to pray there and Muslims are praying five time prayers in the same mosque then it will be considered a legal mosque. This will not go to his wife after his death, but will remain mosque forever.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
