Musannaf Ibn Abi Shaybah 11130 — Reports on the reward for fever

It is narrated from Rabi' bin Umaylah that a Bedouin was with Sayyiduna Ammar (may Allah be pleased with him), and the people mentioned pain and illness in his presence. Sayyiduna Ammar said: "Have you ever complained of illness?" He said: "No." He said: "Then you are not one of us. There is no believer who is put through hardship except that his sins fall away just as the leaves of a tree fall. And the disbeliever is put through hardship, but his example is that of a camel: when it is tied it does not know why it was tied, and when it is released it does not know why it was released."