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." (Using translation from Bukhārī 5667)   

دَخَلْتُ عَلَى رَسُولِ اللهِ ﷺ وَهُوَ يُوعَكُ فَمَسَسْتُهُ فَقُلْتُ يَا رَسُولَ اللهِ إِنَّكَ تُوعَكُ وَعْكًا شَدِيدًا فَقَالَ «إِنِّي أُوعَكُ كَمَا يُوعَكُ رَجُلَانِ مِنْكُمْ» وَفِي الْحَدِيثِ قُلْتُ إِنَّ لَكَ لَأَجْرَيْنِ قَالَ نَعَمْ وَالَّذِي نَفْسِي بِيَدِهِ مَا عَلَى الْأَرْضِ مُسْلِمٌ يُصِيبُهُ أَذًى مِنْ مَرَضٍ فَمَا سِوَى ذَلِكَ إِلَّا حَطَّ اللهُ عَنْهُ خَطَايَاهُ كَمَا تُحُطُّ الشَّجَرَةُ وَرَقَهَا