What is the ruling on a mosque that contains a grave?

Prayer at graves, taking them as mosques, and building mosques over them are innovations that contravene the guidance of the Prophet, peace and blessings be upon him. There are numerous, successively transmitted texts that prohibit this and sternly warn against it. Scholars have explicitly stated the prohibition of building mosques over graves, and they have affirmed that mosques built over the graves of prophets, righteous people, or others must be demolished, and prayer in them is invalid. Ibn al-Qayyim said that a mosque built over a grave should be demolished, for a mosque and a grave cannot coexist in the religion of Islam.