I heard Messenger of Allah ﷺ saying, "Fever is from the heat of Hell, so abate fever with water." (Using translation from Bukhārī 5726)

سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ «الْحُمَّى مِنْ فَيْحِ جَهَنَّمَ فَأَبْرِدُوهَا بِالْمَاءِ»