I heard the Messenger of Allah ﷺ say, "Fever is from the surging heat of Hell, so cool it down with water."
حدثنا عفان حدثنا أبو الأحوص قال حدثنا سعيد بن مسروق عن عباية بن رفاعة
سمعت رسول الله ﷺ يقول إن الحمى فور جهنم فابردوها بالماء
Its chain of transmission is sahih. Its narrators are trustworthy and have been previously mentioned. Abu Ahwas is Salam bin Salim, who is a trustworthy and precise narrator, and has been previously mentioned.The hadith was recorded by Bukhari 4/146 (Al-Shab edition), in the beginning of creation, the description of the fire, and Muslim 4/1733, number 2212, in greetings, every disease has a cure, and Tirmidhi 4/404, number 2074, in medicine, what has been said about cooling fever with water, and he graded it sahih. And Ibn Majah 2/1149, number 3471, and Darimi 2/407, number 2769, and Malik 2/945, number 16, in the eye, ghusl with water for fever.