Hadith 1727
وَحَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الْحُمَّى مِنْ فَيْحِ جَهَنَّمَ فَأَطْفِئُوهَا بِالْمَاءِ " .
Malik related to me from Nafi from Ibn Umar that the Messenger of Allah, may Allah bless him and grant him peace, said, "Fever is from the vehemence of the heat of Jahannam, so put it out with water
Sahih (Salim al-Hilali)
Muwatta Malik 1727 · Book 50, Hadith 17