It is narrated from Abdullah bin Abbas (may Allah be pleased with him) and Aisha (may Allah be pleased with her) that when the Prophet (peace and blessings be upon him) was afflicted with his final illness, he would repeatedly cover his blessed face with a sheet. When he (peace and blessings be upon him) felt discomfort, we would remove the sheet from his face. The Prophet (peace and blessings be upon him) was saying, "May Allah curse the Jews and Christians; they made the graves of their prophets places of prostration." Aisha (may Allah be pleased with her) says that in fact, the Prophet (peace and blessings be upon him) was warning people against this act so that they would not fall into it.