(16) باب قَوْلِ الْمَرِيضِ إِنِّي وَجِعٌ أَوْ وَارَأْسَاهْ، أَوِ اشْتَدَّ بِي الْوَجَعُ
Narrated Ibn Mas`ud:
I visited the Prophet (ﷺ) while he was having a high fever. I touched him an said, "You have a very high fever" He said, "Yes, as much fever as two me of you may have." I said. "you will have a double reward?" He said, "Yes No Muslim is afflicted with hurt caused by disease or some other inconvenience, but that Allah will remove his sins as a tree sheds its leaves."
Reference: Sahih al-Bukhari 5667
In-book reference: Book 75, Hadith 28
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 70, Hadith 571