Hazrat Anas Johani (may Allah be pleased with him) once came to Hazrat Abu Darda (may Allah be pleased with him) and prayed for him, saying, "May Allah keep you safe from every illness and grant you health." Hazrat Abu Darda (may Allah be pleased with him) said, "I heard the Noble Prophet (peace and blessings be upon him) say that a Muslim person continues to suffer from headaches and other illnesses, and his sins are as great as the mountain of Uhud, but these illnesses do not leave him until there is not even a mustard seed's weight of sin left upon him."