The Book of Virtue, Enjoining Good Manners, and Joining of the Ties of Kinship
Ṣaḥīḥ Muslim 6559
مَا مِنْ مُسْلِمٍ يُصِيبُهُ أَذًى مِنْ مَرَضٍ فَمَا سِوَاهُ إِلاَّ حَطَّ اللَّهُ بِهِ سَيِّئَاتِهِ كَمَا تَحُطُّ الشَّجَرَةُ وَرَقَهَا
mā min muslimin yuṣībuhu adhan min maraḍin famā siwāhu illā ḥaṭṭa-Llāh bihi sayyiātihi kamā taḥuṭṭu ash-shajarah waraqahā
Transliteration generated from the Arabic vowel marks
The full narration
Abdullah reported:I visited Allah's Messenger (ﷺ) as he was running a high temperature. I touched his body with my hand and said to him: Allah's Messenger, you are running a high temperature, whereupon Allah's Messenger (ﷺ) said: Yes, it is so. I comparatively have a more severe fever than any one of you. I said: Is it because there is a double reward in store for you? Thereupon Allah's Messenger (ﷺ) said: Yes, it is so. And Allah's Messenger (ﷺ) again said: When a Muslim falls ill, his compensation is that his minor sins are obliterated just as leaves fall (in autumn). In the hadith transmitted on the authority of Zubair there is (no mention of these words):" I touched his body with my hands
Source
Ṣaḥīḥ Muslim · 6559