Excerpt from the book The prophetic medicine by Ibn Al Qayyim
It has been narrated in the Sahihain that the Prophet (pbuh) said:
“Verily Fever- or severe fever- is a breath of the Hell Fire, so cool it using water.
The body benefits from the fever more so than it benefits from taking medicine. This is because, the fever heats up and matures harmful substances, which it could not have done without the fever. Also the fever causes various blockages to open especially those that medicines can not reach.
Accidental type of fevers can be relieved by being submerged into cold water or by drinking cold water. Galinus, one of the renowned doctors, admitted that cold water helps relieve this type of fever.
Fever is usually followed by a diet avoiding improper foods and requires consuming beneficial foods and medicines. The sick person’s body will be cleansed from all impurities and septic elements and materials, having a similar purifying effect as the fire has when it removes the impurity of the iron.
It is also narrated in the Sunan that Abu Hurairah, may Allah be pleased with him said:
Fever was mentioned in the presence of the Prophet Muhammad peace be upon him and a man cursed it.
The Messenger of Allah (pbuh) said,
“Do not curse it, for it removes the sins, just as fire removes the impurity of the iron.” (also refer to Sahih Muslim)
Fever thus helps the body and the heart, Therefore, cursing such a beneficial matter would be an act of injustice and transgression.