"Hadith - Bukhari 7:564

I visited Allah's Apostle while he was suffering from a high fever. I touched him with my hand and said, "O Allah's Apostle! You have a high fever." Allah's Apostle said, "Yes, I have as much fever as two men of you have." I said, "Is it because you will get a double reward?" Allah's Apostle said, "Yes, no Muslim is afflicted with harm because of sickness or some other inconvenience, but that Allah will remove his sins for him as a tree sheds its leaves."