مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3594
Musnad of Abdullah bin Mas'ood
It was narrated that ‘Abdullah said: I entered upon The Messenger of Allah (ﷺ) and he was running a fever. I touched him with my hand and said: O Messenger of Allah, you are running a high fever. The Messenger of Allah (ﷺ) said: “Yes, I am running a fever like two of you.” I said: Then you will have two rewards. The Messenger of Allah (ﷺ) said: “Yes. There is no Muslim who is afflicted with sickness or anything else, but Allah will erase thereby his bad deeds just as trees shed their leaves.”
Musnad Ahmad 3618Its isnad is saheeh, al-Bukhari (5647) and Muslim (2571)]