Ibn Majah

Benefits and Issues:
➊
The connection of the sick person with the Fire of Hell is unseen and spiritual. Its reality cannot be known. Or it means that it reminds one of Hell. Or, just as the joys and comforts of this world have a certain relation to the blessings of Paradise, similarly, sorrow and pain have a connection with Hell.

➋
The remedy for heat is water. In most types of fever, the use of water is beneficial.

➌
The method of using water is not specified in this hadith; there can be various ways of using it. For example, drinking water, placing wet cloths on the body, or performing ritual bath (ghusl), as the Messenger of Allah (sallallahu alayhi wa sallam) performed ritual bath (ghusl) in the last days of his blessed life so that the heat would lessen and he could join the congregational prayer. Especially in hot regions, fever is generally due to the intensity of heat. Therefore, treating it with water is appropriate. Asma bint Abi Bakr (radi Allahu anha) used to pour water into the collar of a woman suffering from fever so that the body would cool down, and she used to say that the Messenger of Allah (sallallahu alayhi wa sallam) commanded us to cool it (the fever) with water. (Sahih al-Bukhari, Book of Medicine, Chapter: Fever is from the heat of Hell, Hadith: 5724)