From Sahih Muslim (Hadith 7042):
Iyas reported on the authority of his father:We went along with Allah's Messenger (ﷺ) to visit a person suffering from fever. When I placed my hand upon him, I said: By Allah, I have never seen, till this day, a person running higher temperature than he. Thereupon Allah's Apostle (ﷺ), turning his face to his companions, said: May I not inform you of a severer temperature than this which these two persons would run on the Day of Resurrection? And they were two hypocrites riding upon the camel turning their back towards (the Muslims)
Reference: Muslim 7042