Sayyiduna Abdullah (may Allah be pleased with him) said: I came to the Prophet (peace and blessings be upon him) while he (peace and blessings be upon him) had a fever. I touched him (peace and blessings be upon him) and said: O Prophet of Allah! You have a very high fever. He (peace and blessings be upon him) said: "Yes, I suffer fever as much as two men among you." I said: Your (peace and blessings be upon him) reward will also be double. He (peace and blessings be upon him) said: "Yes. By the One in whose hand is my soul, there is no Muslim on the earth who is afflicted by any hardship or illness but that Allah Almighty wipes away his sins just as a tree sheds its leaves."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13416