Musnad Ahmad 938:55

Bahz narrated to us, Shu'bah narrated to us, he said: 'Adi ibn Thabit informed me, from 'Abdullah ibn Yazid, from Zayd ibn Thabit: That the Messenger of Allah (ﷺ) went out to Uhud, and some people who had gone out with him returned. The companions of the Messenger of Allah (ﷺ) were divided into two groups regarding them; one group said: "Kill them," and one group said: "No." Ibn Ja'far said: The people were divided into two groups regarding them; a group saying: "Kill them," and a group saying: "No." Bahz said: Then Allah, the Almighty and Majestic, revealed: {So what is [the matter] with you [becoming] two groups regarding the hypocrites?} [An-Nisa: 88]. The Messenger of Allah (ﷺ) said: "It is Tayyibah (Madinah), and it expels the filth, just as the fire expels the filth of silver." 'Affan narrated it to us, and he said in it: I heard 'Abdullah ibn Yazid, and he mentioned the meaning of the hadith of Bahz.