Hadith 14:258
Abu Bakr narrated to us, he said: Ibn Numayr and Muhammad ibn Bishr narrated to us, they said: Ubaydullah narrated to us, from Nafi’, from Ibn Umar, from the Prophet (peace and blessings of Allah be upon him), who said: "Indeed, the intensity of fever is from the scorching heat of Hell, so cool it with water."
حدثنا أبو بكر قال حدثنا بن نمير ومحمد بن بشر قالا حدثنا عبيد الله عن نافع عن بن عمر عن النبي صلى الله عليه وسلم قال إن شدة الحمى من فيح جهنم فأبردوها بالماء