The Prophet ﷺ said, "When a believer falls ill, it purifies him just as a blacksmith's furnace removes the impurities from iron."
عن النبي ﷺ قال: إذا اشتكى المؤمن أخلصه ذلك كما يخلص الكير خبث الحديد.
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Ibn Hibban (2936) and Qudai in Musnad Shihab (1407) both narrated it from the hadith of Ibn Abu Dhib, from Zuhri, from Urwa, from Ayesha, and I have recorded it. Tabarani also narrated it in Awsat (1155, Majma Bahrayn), as did Qudai (1406) and Ibn Abu Dunya in Illness and Expiations (90), all of them from the hadith of Ibn Abu Dhib, from Hisham bin Urwa, from his father, from Ayesha, in similar wording. Its chain is sahih, and it is not weakened by what Bukhari narrated in Adab al-Mufrad (497), where he inserted between Ibn Abu Dhib and Ibn Shihab the name "Jubayr bin Abu Salih." Dhahabi said of this Jubayr, "It is not known who he is." The chain is sahih without him, and indeed that is the more correct version, since the majority of the narrators from Ibn Abu Dhib omitted Jubayr bin Abu Salih.As for what was narrated from Fatimah Khuzaiyah, who had met most of the companions of the Prophet ﷺ, that the Messenger of Allah ﷺ visited a woman from the Ansar who was in pain, and he said to her, "How do you find yourself?" She said, "Well, Messenger of Allah, though the mother of fever has been afflicting me, meaning she was burning with fever." The Messenger of Allah ﷺ said to her, "Be patient, for it removes the impurity of a person just as the bellows remove the impurity from iron." This is mursal, as is clear. It was narrated by Abdul-Razzaq (30306), and through his route by Tabarani in Kabir (24/405), from Mamar, from Zuhri, who said, "Fatimah Khuzaiyah related to me," and he then recounted the hadith. Haythami said in Majma (2/307), "Its narrators are the narrators of sahih." Fatimah Khuzaiyah, as indicated by Zuhri's statement, was a successor, and accordingly her narration from the Prophet ﷺ is mursal.