"For fever, and all pains, the Prophet ﷺ would teach them to say: Bismillahil-Kabir; a'udhu billahil-'Azimi min sharri kulli 'irqin na'arin, wa min sharri harrin-nar. (In the name of Allah the Great, I seek refuge with Allah the Magnificent from the evil of every gushing vein, and from the evil of the heat of the Fire)"  

أَنَّ النَّبِيَّ ﷺ كَانَ يُعَلِّمُهُمْ مِنَ الْحُمَّى وَمِنَ الأَوْجَاعِ كُلِّهَا أَنْ يَقُولَ بِسْمِ اللَّهِ الْكَبِيرِ أَعُوذُ بِاللَّهِ الْعَظِيمِ مِنْ شَرِّ كُلِّ عِرْقٍ نَعَّارٍ وَمِنْ شَرِّ حَرِّ النَّارِ