Abdullah bin 'Umar said, the Prophet, may Allah bless him, said, 'Fever is from the heat of Hell. Put it out (cool it) with water.' (Sahih Bukhari, Hadith 3024)
Some fellows ask as to what is the connection between fever and the hell. The Hadith itself does not say it explicitly.
General Meaning of the Hadith:
Certain scholars like Hafiz Ibn Hajr al-Asqalani and al-Manawi have said that the Hadith means, heat of fever is like the heat of hell and it works as an admonition to the people against its torment.
Zainuddin Muhammad al-Manawi (d. 1031 A.H.) wrote:
“And it is in the likeness of hell fire in that it torments and afflicts the body. And its significance is in its being a reflection and a shadow of the archetype from hell which is brought as evidence unto people (to be mindful of the life hereafter). And they are asked to reflect on it just like joy and pleasures are brought to show the blessings of the Paradise.” (Faidh al-Qadir fi Sharah Jami’ al-Saghir, 3/409 Hadith 3838)
This is the significance for everyone. However another Hadith narration highlights a meaning of this Hadith specifically relevant to true believers.
Especially for the believers:
The Messenger of Allah –may Allah bless him- said: “Fever is from the bellows of the Hell. So whatever of it afflicts a believer is his share from the hellfire.” (Musnad Ahmad, Hadith 22328. Authenticated by Shu’aib Arnaut)
One can understand this better if he reads it along with the following narration.
Umayyah asked Aisha –may Allah be pleased with them both- to explain the verses, “If you disclose what is in your hearts or conceal it, Allah shall hold you accountable for it” (2: 284) and “Whoever does evil shall be requited for it” (4: 123) Aisha said that no one had asked her about these verses since she had asked Allah’s Messenger –may Allah bless him- about these. He said: “This is how Allah afflicts His slaves in difficulties, like fever or misfortune - even loss of something that he places in his shirt pocket and grieves for it. Thus, the slave comes out of his sins just as gold comes out the bellows.” (Jami’ al-Tirmidhi, Hadith 2991. Classified as Hasan by al-Tirmidhi)
Cooling with water:
The mention of cooling with water is to do away with the physical effect of fever only.
In conclusion, the Hadith tells us that physical effect of fever is simply a reflection of the hellfire and the purpose is to warn people against transgressing Allah’s commandments.
And for the true believers the significance is that it is a source of expiation of their sins so that when they meet their Lord on the Day of Recompense they are pure, free from sins like pure gold free from all dross. And thus they will not be subjected to any punishment in the hell.
Indeed Allah knows the best!