Ibn Majah

Hadith Commentary:
Due to its heat, fever has been likened to the steam of Hellfire, and the Messenger of Allah (sallallahu alayhi wa sallam) spoke the truth. Enduring fever with patience is itself a source of reward, and supplicating for well-being is equally correct.
The Prophet (sallallahu alayhi wa sallam) would frequently supplicate:
"Allahumma inni as'aluka al-'afwa wa al-'afiyah" — O Allah! I ask You for pardon and well-being.

Hadith Commentary:
In this hadith, the method of using water is not specified.
There can be various ways of using it, for example:
Drinking water or placing wet cloths on the body, applying ice, or performing ritual bath (ghusl), as the Messenger of Allah (sallallahu alayhi wa sallam) performed a ritual bath in the last days of his blessed life so that the heat would subside somewhat and he could perform prayer in congregation.
In hot regions, fever generally occurs due to the intensity of heat; therefore, treating it with water is appropriate.
In one narration, Zamzam water is mentioned.
(Sahih al-Bukhari, Book of the Beginning of Creation, Hadith: 3261)
But this specification is incidental, because Zamzam water was abundantly available in Makkah, and the mentioned incident also took place in Makkah.
All types of water are beneficial for fever.
Doctors also advise the use of ice packs in this regard; in any case, doing so reduces the severity of the fever.

Hadith Commentary:
➊
Taking a ritual bath (ghusl) with cold water is beneficial in bilious (safrawi) fever.
Nowadays, in cases of high fever, doctors advise placing cloths cooled with ice on the patient’s head and recommend washing the patient’s hands and feet with cold water. However, this treatment is not for every type of fever; rather, it is better to do so in fevers caused by heat.
The Messenger of Allah (sallallahu alayhi wa sallam) prescribed this treatment for the people of Hijaz and its surrounding areas because they frequently suffered from fevers due to heat. Therefore, for such patients, taking a ritual bath (ghusl) with cold water is beneficial.

➋
These ahadith do not specify the method of cooling the fever, but when a woman suffering from fever was brought to Asma bint Abi Bakr (radi Allahu anha), she used to pour water on her chest.
(Sahih al-Bukhari, Book of Medicine, Hadith: 5224)
Since this lady was the elder sister of Aisha (radi Allahu anha) and often used to visit the Messenger of Allah (sallallahu alayhi wa sallam), on this basis she knew this matter better than others.
Further details regarding this will be mentioned in the Book of Medicine.
By the permission of Allah, the Exalted.

Hadith Commentary: Benefits and Issues: Fever and every pain originate and stem from Hell, and every pleasure and joy originate and stem from Paradise. In this way, for a believer, it is as if, in this world, it is an expiation for sins, by which he will be saved from the punishment of Hell. For evil people, it is a cause of pain and suffering. During fever, bathing (ghusl) or swimming in water is considered extremely beneficial in many types of fever according to both ancient and modern physicians. Even today, in the summer season, when the fever is extremely high, doctors have ice packs placed on the head and have the entire body wiped with a towel soaked in ice water. However, this should be done only on the advice of an expert physician or doctor, because this treatment is not suitable for every place, every season, every person, or every type of fever. In fact, the treatment for the same person changes with age, season, and diet. For details, see (Takmila, vol. 4, pp. 343-344).

Takhrij al-Hadith: [وأخرجه البخاري 5723، ومسلم 220/79، من حديث مالك به المرفوع فقط ورواه الجوهري 704 عن ابن وهب عن مالك نحوه]
Jurisprudential Points:
➊ There are some fevers (such as typhoid) in which cooling the body with water or ice, etc., is beneficial.
➋ One should always supplicate to Allah alone.
➌ The coming of hardships and trials upon a believer in this world is a means for the elevation of his ranks, provided that he demonstrates patience and gratitude.