What is the ruling on burying the dead in mosques?

The Prophet (peace be upon him) forbade burial in mosques and the building of mosques over graves, and he cursed those who did so. This is because it imitates the Jews and Christians, and it is a means to Shirk (associating partners with Allah) and believing that the occupants of the graves can bring benefit or harm. Therefore, mosques must be free of graves and built upon pure monotheism for Allah, as Allah the Almighty says: (And the mosques are for Allah, so do not invoke anyone along with Allah).