It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) went to visit a Bedouin who was ill, and whenever the Prophet (peace and blessings be upon him) visited a sick person, he would recite this supplication: «لا بأس طهور إن شاء الله» "No harm, it is a purification, if Allah wills." The Bedouin said: Is it a purification? Never! It is a fever that has attacked an old man to drive him to the graveyard. The Prophet (peace and blessings be upon him) said: "Then it shall be as you say."