"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)" (Using translation from Tirmidhī 2075)
أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُعَلِّمُهُمْ مِنَ الْأَوْجَاعِ وَمِنَ الْحُمَّى أَنْ يَقُولَ «بِسْمِ اللَّهِ الْكَبِيرِ نَعُوذُ بِاللَّهِ الْعَظِيمِ مِنْ شَرِّ عِرْقِ نَعَّارٍ وَمَنْ شَرِّ حَرِّ النَّارِ»