Is it permissible to accept money from a Christian man as a donation for building a mosque?

The Sharia has permitted accepting gifts from a disbeliever, and thus it is permissible to accept their donation for building a mosque. It is not a condition that the source of the money used to construct mosques be halal. If a person has unlawful money and wishes to repent from it, but cannot identify its rightful owner, then they should spend it on general Muslim interests, such as mosques, bridges, and the like.