Sahih al-Bukhari 5648
صحيح البخاري#5648SahihNarrated `Abdullah:I visited Allah's Messenger (ﷺ) while he was suffering from a high fever. I said, "O Allah's Messenger (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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 75:8