كتاب العين
50  
The Evil Eye

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."

وَحَدَّثَنِي مَالِكٌ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ الْحُمَّى مِنْ فَيْحِ جَهَنَّمَ فَأَطْفِئُوهَا بِالْمَاءِ ‏"‏ ‏.‏
Sunnah.com reference : Book 50, Hadith 17
USC-MSA web (English) reference : Book 50, Hadith 16
Arabic reference : Book 50, Hadith 1730