The Messenger of Allah ﷺ said, "There is no Muslim man or Muslim woman, no believing man or believing woman, who falls ill except that Allah erases some of their sins because of it."
قال رسول الله ﷺ: ما من مسلم ولا مسلمة، ولا مؤمن ولا مؤمنة، يمرض مرضا إلا حط الله عنه من خطاياه.
Imam Ahmad (15146) and Abu Yaala (2305) both narrated it via Amash, from Abu Sufyan, from Jabir, mentioning something similar, and the wording given is Ahmad's. Bukhari also narrated it from this same route in Adab al-Mufrad (508), except that he said in it, "Allah would settle his sins on his behalf."Abu Sufyan is Talha bin Nafi, who is "sincere and trustworthy." This narration is corroborated in Ahmad (14725), Bazzar (758 - Kashf), and Ibn Hibban in his Sahih (2927), who narrated it from another route, from Abu Zubayr, from Jabir. Ibn Hibban's wording is, "Allah would remove his sins by that, just as a leaf falls from a tree."Bazzar said, "We do not know of a better route for it from Jabir than this one."Haythami said in Majma (2/301), "Ahmad, Abu Yaala, and Bazzar narrated it, and Ahmad's narrators are the narrators of the Sahih."