Sahih Muslim Book 45, Hadith 56
This hadith has been narrated on the authority of A'mash through other chains of transmitters.
'A'isha reported, I did not see anyone else being afflicted with more severe illness than Allah's Messenger (ﷺ). In the narration transmitted by 'Uthman there is a slight variation of wording.
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."