Narrated from Sayyiduna Ka'b bin Malik (may Allah be pleased with him) that a man came to the Noble Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) asked him: "How long have you had a fever? It is an increase of heat between the skin and flesh." He replied: "It is such an affliction that I have never suffered from it." The Prophet (peace and blessings be upon him) said: "The example of a believer is like that of a soft, delicate, and fresh crop which is sometimes red and sometimes yellow."

Mu’adh narrates that he came to visit Sayyiduna Abu Darda’ (may Allah be pleased with him), and when he greeted him with salam, he (Abu Darda’) said: Remain with health, not with illness, and he supplicated this three times. Then he said: I heard the Messenger of Allah (peace and blessings be upon him) say: A Muslim remains afflicted with fever and headaches and similar illnesses, while he has sins as great as Mount Uhud, but because of these illnesses, his sins fall away from him such that not even the weight of a mustard seed of sin remains upon him.

Sayyiduna Abu Umamah narrates that the Messenger of Allah, peace and blessings be upon him, said: Fever is the bellows of Hell; for any believer who falls ill, it will be in exchange for his portion of Hell.

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, went to visit a sick person who had a fever. The Prophet, peace and blessings be upon him, said to him: Rejoice, for Allah Almighty says: (This fever) is My fire, which I impose upon My believing servant in this world so that it may become a substitute for the punishment of the fire in the Hereafter.

It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both), he says: Fever sought permission to come to the Prophet Muhammad (peace and blessings be upon him). The Prophet (peace and blessings be upon him) said: Who is this? It said: I am Umm Miladim (Mother of Heat). The Prophet (peace and blessings be upon him) ordered that it be transferred to the people of Quba. So they were afflicted with it in such abundance that only Allah knows its extent. Those people came to the Prophet (peace and blessings be upon him) complaining about it. The Prophet (peace and blessings be upon him) said: What do you want? If you want me to pray to Allah to remove it from you, then fine; and if you want it to be a purifier for you, (then let it remain with you). They said: O Messenger of Allah! Does it purify from sins? The Prophet (peace and blessings be upon him) said: Yes. They said: Then let it remain.