Sayyida Aisha (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) had a black cloak. When his illness intensified, he (peace and blessings be upon him) would sometimes cover his face with it and sometimes remove it from his face, and he would say: May Allah destroy those people who made the graves of their prophets into mosques. He (peace and blessings be upon him) was declaring this act forbidden for his ummah.