Sahih Muslim | Book 38 | Hadith Number 6695
Narrated by Iyas
Iyas reported on the authority of his father: We went along with Allah's Messenger (may peace be upon him) 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 (may peace be upon him), 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).