The Prophet ﷺ said, "Fever comes from the bellows of Hell, so whatever of it afflicts the believer is his share of the Fire."
حدثنا يزيد هو ابن هارون أخبرنا محمد بن مطرف عن أبي الحصين عن أبي صالح الأشعري
عن النبي ﷺ قال الحمى من كير جهنم فما أصاب المؤمن منها كان حظه من النار
Its chain of transmission is hasan, but there is a question mark over it. They said, Abu Salih Ashari is unknown, though Ajli deemed him reliable. And they said, Abu Husayn Filastini is unknown, though it has been said that he is in fact Marwan bin Ruba Taghlibi, who is acceptable. It is corroborated by the hadith about fever being from the exhalation of Hell, which preceded at 4719, 5576, and 17199.