I visited Messenger of Allah ﷺ while he was suffering from a high fever. I said, "O Messenger of Allah ﷺ! You have a high fever." He said, "Yes, I have as much fever as two men of you." I said, "Is it because you will have a double reward?" He said, "Yes, it is so. No Muslim is afflicted with any harm, even if it were the prick of a thorn, but that Allah expiates his sins because of that, as a tree sheds its leaves." (Using translation from Bukhārī 5648)   

دَخَلْتُ عَلَى رَسُولِ اللهِ ﷺ وَهُوَ يُوعِكُ وَعْكًا شَدِيدًا قُلْتُ يَا رَسُولَ اللهِ إِنَّكَ تُوعِكُ وَعْكًا شَدِيدًا ذَلِكَ بِأَنَّ لَكَ أَجْرَيْنِ قَالَ «أَجَلْ إِنَّهُ كَذَلِكَ مَا مِنْ مُسْلِمٍ يُصِيبُهُ أَذًى مِنْ مَرَضٍ فَمَا سِوَاهُ إِلَّا كَفَّرَ اللهُ بِهِ سَيِّئَاتِهِ كَمَا تَحُطُّ الشَّجَرَةُ وَرَقَهَا»  

"I have not seen ailment effecting anyone worse than upon the Messenger of Allah ﷺ." (Using translation from Tirmidhī 2397)  

«مَا رَأَيْتُ الْوَجَعَ عَلَى أَحَدٍ أَشَدَّ مِنْهُ عَلَى رَسُولِ اللهِ ﷺ»