The Ruling on Praying in a Mosque Built with Forbidden Wealth

The third question in the letter from our brother Khalid Ali of the Democratic Republic of Sudan states: There is a mosque founded by a man who works with amulets and veils, and vows are brought to him and drums are beaten in his house. They claim that he treats the insane with drums, amulets, and the like. Does this wealth, which he earned and used to found the mosque, make the mosque one founded on other than piety, like the Mosque of Dirar? Please inform us, may Allah reward you? And is it permissible to pray behind him? Please inform us, may Allah reward you?
Answer: One does not pray behind this man because his outward appearance indicates corruption in creed. As for the mosque, there is no harm in praying in it, and one does not look at its funding. Rather, one prays in it, and the people of the Sunnah and the community pray in it until the people of evil, open sinfulness, and corruption distance themselves from it. As for this man whose work is this, one does not pray behind him because his outward appearance indicates corruption in creed and lack of uprightness. May Allah grant everyone health and safety.