The Prophet ﷺ said regarding fever, "Cool it down with water, for it comes from the blast of Hellfire."
عن النبي ﷺ قال في الحمى: أبردوها بالماء؛ فإنها من فيح جهنم.
Ahmad (21886) narrated it from Muhammad bin Jafar, who said, Shubah narrated to us, from Ansari, who said, I heard Ibn Abu Bashir and the daughter of Abu Bashir both narrating from their father, Abu Bashir, and he mentioned it.Its isnad is hasan. Ibn Abu Bashir and the daughter of Abu Bashir are both unknown, but each strengthens the other. Moreover, there is nothing in their hadith that would be objected to, rather it has a well-established basis.