I never saw anybody suffering so much from sickness as Messenger of Allah ﷺ.  

مَا رَأَيْتُ أَحَدًا أَشَدَّ عَلَيْهِ الْوَجَعُ مِنْ رَسُولِ اللَّهِ ﷺ  

I entered upon the Messenger of Allah ﷺ while he was suffering from a high fever. I said, "O Messenger of Allah ﷺ, you have a very 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 the prick of a thorn or something greater except that Allah expiates his sins because of it just as a tree sheds its leaves."  

دَخَلْتُ عَلَى رَسُولِ اللَّهِ ﷺ وَهْوَ يُوعَكُ، فَقُلْتُ: يَا رَسُولَ اللَّهِ، إِنَّكَ تُوعَكُ وَعْكًا شَدِيدًا! قَالَ: «أَجَلْ، إِنِّي أُوعَكُ كَمَا يُوعَكُ رَجُلاَنِ مِنْكُمْ۔» قُلْتُ: ذَلِكَ أَنَّ لَكَ أَجْرَيْنِ؟

قَالَ: «أَجَلْ، ذَلِكَ كَذَلِكَ: مَا مِنْ مُسْلِمٍ يُصِيبُهُ أَذًى شَوْكَةٌ فَمَا فَوْقَهَا إِلاَّ كَفَّرَ اللَّهُ بِهَا سَيِّئَاتِهِ كَمَا تَحُطُّ الشَّجَرَةُ وَرَقَهَا۔»  

(the wife of the Prophet) Messenger of Allah ﷺ said, "No calamity befalls a Muslim but that Allah expiates some of his sins because of it, even though it were the prick he receives from a thorn."  

أَنَّ عَائِشَةَ ؓ زَوْجَ النَّبِيِّ ﷺ قَالَتْ قَالَ رَسُولُ اللَّهِ ﷺ مَا مِنْ مُصِيبَةٍ تُصِيبُ الْمُسْلِمَ إِلاَّ كَفَّرَ اللَّهُ بِهَا عَنْهُ حَتَّى الشَّوْكَةِ يُشَاكُهَا  

The Prophet ﷺ said, "No fatigue, nor disease, nor sorrow, nor sadness, nor hurt, nor distress befalls a Muslim, even if it were the prick from a thorn, except that Allah expiates some of his sins for that."  

عَنِ النَّبِيِّ ﷺ قَالَ: «مَا يُصِيبُ الْمُسْلِمَ مِنْ نَصَبٍ، وَلاَ وَصَبٍ، وَلاَ هَمٍّ، وَلاَ حُزْنٍ، وَلاَ أَذًى، وَلاَ غَمٍّ، حَتَّى الشَّوْكَةِ يُشَاكُهَا، إِلاَّ كَفَّرَ اللَّهُ بِهَا مِنْ خَطَايَاهُ۔»  

Ibn ʿAbbas said to me, "Shall I show you a woman of the people of Paradise?" I said, "Yes." He said, "This black lady came to the Prophet ﷺ and said, 'I get attacks of epilepsy and my body becomes uncovered; please invoke Allah for me.' The Prophet ﷺ said (to her), 'If you wish, be patient and you will have (enter) Paradise; and if you wish, I will invoke Allah to cure you.' She said, 'I will remain patient,' and added, 'but I become uncovered, so please invoke Allah for me that I may not become uncovered.' So he invoked Allah for her." Narrated 'Ata: That he had seen Um Zafar, the tall black lady, at (holding) the curtain of the Kaʿba.  

أَلاَ أُرِيكَ امْرَأَةً مِنْ أَهْلِ الْجَنَّةِ؟ قُلْتُ: بَلَى۔ قَالَ: هَذِهِ الْمَرْأَةُ السَّوْدَاءُ أَتَتِ النَّبِيَّ ﷺ فَقَالَتْ: إِنِّي أُصْرَعُ وَإِنِّي أَتَكَشَّفُ، فَادْعُ اللَّهَ لِي۔ قَالَ: «إِنْ شِئْتِ صَبَرْتِ وَلَكِ الْجَنَّةُ، وَإِنْ شِئْتِ دَعَوْتُ اللَّهَ أَنْ يُعَافِيَكِ۔» فَقَالَتْ: أَصْبِرُ۔ فَقَالَتْ: إِنِّي أَتَكَشَّفُ، فَادْعُ اللَّهَ أَنْ لاَ أَتَكَشَّفَ۔ فَدَعَا لَهَا۔