Silsilat al-Ahadith al-Sahihah

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

It is narrated from Sayyiduna Uthman bin Affan (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "For the believer, fever is a substitute for his share of the Fire on the Day of Resurrection."

Sayyiduna Abu Umamah narrates that the Messenger of Allah (peace and blessings be upon him) said: "Fever is the bellows of Hell; whichever believer falls ill, it will be in place of his share from the people of Hell."