حَدَّثَنَا يَحْيَى عَنْ عُبَيْدِ اللَّهِ حَدَّثَنِي نَافِعٌ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ الْحُمَّى مِنْ فَيْحِ جَهَنَّمَ فَأَبْرِدُوهَا بِالْمَاءِ
مسند امام احمد بن حنبل · Hadith 4719
It was narrated from 'Abdullah ibn 'Umar from the Prophet (PBUH)"Fever is from the heat of Hell, so cool it down with water."
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020