The Messenger of Allah ﷺ said, "The likeness of the believing servant when illness or fever strikes him is like that of a piece of iron placed in the fire. Its impurities are removed, and its purity remains."
قال رسول الله ﷺ: مثل العبد المؤمن حين يصيبه الوعك، أو الحمى، كمثل حديدة تدخل النار، فيذهب خبثها، ويبقى طيبها.
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Bazzar narrated it (756 - Kashf) from Yusuf bin Abu Yazid, who said, Saeed bin Abu Maryam told us, from Nafi bin Yazid, Jafar bin Rabia told me, from Ubaydullah bin Abdul-Rahman bin Saaib, that Abdul-Hameed bin Abdul-Rahman bin Azhar reported from his father, Abdul-Rahman bin Azhar, mentioning something similar.Hakim also narrated it (1/73, 3/48), as did Ibn Abu Dunya in "Al-Marad wal-Kaffarat" (24), both by way of Saeed bin Abu Maryam, with the same wording. Hakim said in the first place, "This is a hadith sahih in isnad, and the two of them (Bukhari and Muslim) did not include it. What I hold is that they left it out because Abdul-Hameed was alone in narrating from his father." And he said in the second place, "Sahih in isnad, its narrators are from Madinah and Egypt, and the two of them did not include it."However, Haythami said in "Al-Majma" (2/302), "Bazzar and Tabarani narrated it, and it contains someone who is not known."I say, perhaps he means by this Abdul-Hameed bin Abdul-Rahman, whom Ibn Abu Hatim mentioned in "Al-Jarh wat-Tadil" (6/15) without saying anything about him. However, Ibn Hibban mentioned him in "Al-Thiqat" (5/127) and said, "One of the people of Madinah, he narrates from his father and a group of the Tabiin, and the people of Madinah narrated from him." This means he was known among the people of Madinah as someone who could be narrated from, and the people of Madinah would not narrate except from someone they knew.Ubaydullah bin Abdul-Rahman bin Saaib was one of the people of Madinah, and he narrated from Abdul-Hameed and others. Ibn Jurayj narrated from him, as did Nafi bin Yazid, once through an intermediary, as here, and another time without an intermediary. He is also among those Ibn Hibban mentioned in "Al-Thiqat" (2/189).Abdul-Rahman bin Azhar had companionship with the Prophet ﷺ and was present at Hunayn with him. Ibn Saad mentioned him in the seventh generation among those who retained knowledge from the Messenger of Allah ﷺ while still young, saying, "He was close in age to Abdullah bin Abbas, and he lived until the sedition of Ibn Zubayr." He is also mentioned in the Sahihayn regarding the two rakahs after Asr.It is to these narrators that Hakim referred when he said, "Its narrators are from Madinah." Narrators of this caliber have their hadith graded hasan when they do not contradict others.As for what was narrated from Abu Hurairah, who said, Fever was mentioned in the presence of the Messenger of Allah ﷺ, and a man cursed it, so the Prophet ﷺ said, "Do not curse it, for it removes sins just as fire removes the impurity from iron." This is daif. Ibn Majah narrated it (3469) from Abu Bakr bin Abu Shayba, who said, Waki told us, from Musa bin Ubayda, from Alqama bin Marthad, from Hafs bin Ubaydullah, from Abu Hurairah, mentioning the hadith.Musa bin Ubayda is Ibn Nashit Rabadi Madani, considered daif by the majority of scholars. Hafiz described him in "Al-Taqrib" as "daif."