Is it permissible to pray in a mosque that contains a shrine, whether it is at the front or to the side of it?

Praying at graves, turning them into mosques, and building structures over them are innovations that contravene the guidance of the Prophet, peace and blessings be upon him. Many texts prohibit such practices. Mosques built over the graves of prophets or righteous individuals must be removed, and prayer in them is invalid. Ibn al-Qayyim stated that a mosque built over a grave must be demolished, for a mosque and a grave cannot coexist in Islam.