Ibn Mas'ud (May Allah be pleased with him) reported:
I visited the Prophet ﷺ when he was suffering fever. I said, "You seem to be suffering greatly, O Messenger of Allah." The Prophet ﷺ replied, "Yes, I suffer as much as two persons." I said, "Is that because you have a double reward?" He replied that that was so and then said, "No Muslim is afflicted by a harm, be it the pricking of a thorn or something more (painful than that), but Allah thereby causes his sins to fall away just as a tree sheds its leaves".

[Al-Bukhari and Muslim].

وعن ابن مسعود رضي الله عنه قال: دخلت على النبي ﷺ وهو يوعك فقلت: يارسول الله إنك توعك وعكاً شديداً قال: "أجل إني أوعك كما يوعك رجلان منكم" قلت: ذلك أن لك أجرين ؟ قال: "أجل ذلك كذلك ما من مسلم يصيبه أذى؛ شوكة فما فوقها إلا كفر الله بها سيئاته ، وحطت عنه ذنوبه كما تحط الشجرة ورقها" ((متفق عليه)) .