Yahya related to me from Malik from Hisham ibn Urwa from his father that the Messenger of Allah ﷺ said, "Fever is from the vehemence of the heat of Jahannam, so cool it with water."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِنَّ الْحُمَّى مِنْ فَيْحِ جَهَنَّمَ فَابْرُدُوهَا بِالْمَاءِ