The Prophet Muhammad ﷺ said: "Fever is from the heat of Hell, so cool it with water." (Narrated by Al-Bukhari, no. 5724, and Muslim, no. 2209).
This hadith, narrated by Aisha (may Allah be pleased with her), was long interpreted literally. Modern science has revealed its profound medical wisdom.
Fever is in fact a defensive reaction of the body: the rise in body temperature activates the immune system and helps fight infections. However, excessive fever can be dangerous, especially in children, and can cause seizures or damage.
Modern medicine indeed recommends lowering high fever through physical means: lukewarm or cold baths, cold water compresses, hydration. This approach, called "external cooling," is used in hospitals worldwide to treat hyperthermia.
The hadith thus combines two truths: fever is a beneficial defense mechanism (a "heat" that fights disease), but it must be controlled through cooling to avoid its dangers. This nuanced understanding, fourteen centuries old, is in perfect agreement with modern medicine.