as well as al-Nasāʾī (2/204) and Aḥmad (3/292, 306, 307, 365, 385, 392, 393), through the narration of Jābir ibn ʿAbd Allāh:

“A Bedouin pledged allegiance to the Messenger of Allah ﷺ upon Islam. Afterward, the Bedouin was stricken with fever in Madinah, so he came to the Messenger of Allah ﷺ and said, ‘O Messenger of Allah, release me from my pledge.’ The Messenger of Allah ﷺ refused. He returned and said, ‘Release me from my pledge,’ and again he refused. A third time he said, ‘Release me from my pledge,’ but the Prophet ﷺ still refused. The Bedouin then departed, whereupon the Messenger of Allah ﷺ …” — and he related the remainder of the report.

Al-Tirmidhī remarked, “A ḥadīth that is ḥasan (good).”

This report is corroborated by a narration from Zayd ibn Thābit ﵁. Concerning the verse, “So why are you two groups concerning the hypocrites?” (Q 4:88), he said:

“Some people from among the Prophet’s Companions turned back on the Day of Uḥud (in another wording: from Uḥud). The rest of the Muslims split into two parties regarding them: one party said, ‘Kill them,’ while the other said, ‘Do not.’ Then Allah revealed the verse, ‘So why are you two groups concerning the hypocrites?’ He (Zayd) added: ‘Madinah is pure, and it expels its impurities just as fire removes the dross of iron.’”

218 – “Madinah is pure, and it expels impurities just as fire removes the dross of iron.”

Al-Bukhārī recorded it (4/77–78, 8/206); Muslim (9/155–156); al-Tirmidhī (4/89–90); and Aḥmad (6/184, 187, 188) through the route of ʿAbd Allāh ibn Yazīd al-Khaṭmī, from Zayd ibn Thābit. Al-Tirmidhī said, “A ḥadīth that is ḥasan ṣaḥīḥ (good and authentic).”

The scholars explain that “the dross of iron” means its dirt and filth, which the fire drives out of it.

The Qāḍī commented: “What appears stronger is that this (purging effect) was peculiar to the era of the Prophet ﷺ, for in those days no one could endure the hardship of migration….”