One of the governors insulted Ali, so Zayd bin Arqam stood up and said, "Do you not know that the Messenger of Allah ﷺ forbade insulting the dead? Why then do you insult Ali when he has already died?"
سب أمير من الأمراء عليا فقام زيد بن أرقم فقال: أما أن قد علمت أن رسول الله ﷺ نهى عن سب الموتى، فلم تسب عليا وقد مات.
Imam Ahmad narrated it (19315) from Waki, who said, Masaar told us, from Abu Ayub the freedman of the Banu Thalaba, from Qutba bin Malik, who mentioned it. Tabarani also related it in Al-Kabir (5/188) through the route of Imam Ahmad.Abu Ayub is Hajjaj the freedman of Banu Thalaba, as is made explicit in the narration of Imam Ahmad (19288), where he narrated it from Muhammad bin Bishr, who said, Masaar told us, from Hajjaj the freedman of Banu Thalaba, from Qutba bin Malik, the uncle of Ziyad bin Alaqa, who said, Mughira bin Shuba spoke ill of Ali, so Zayd bin Arqam said, and then he related the hadith.Hajjaj Abu Ayub is among the men listed in Al-Tajil (1232), and he is majhul (unknown), as stated by Husayni. However, Tabarani (5/188) and Hakim (1/384-385) both narrated it through the route of Amr bin Muhammad bin Abu Razeen, who said, Shuba told us, from Ziyad bin Alaqa, from his uncle (meaning Qutba bin Malik), that Mughira bin Shuba insulted Ali bin Abu Talib, so Zayd bin Arqam stood up to him, and then he related the hadith.Hakim said, "Sahih according to the criterion of Muslim, though the two of them did not include it." I say, this is a mistake on his part, for Amr bin Muhammad bin Abu Razeen is not among the men of Muslim, but is only among the men of Tirmidhi, as Hafiz pointed out in Al-Taqrib. Ibn Hibban mentioned him among the trustworthy narrators and said, "He may have erred at times."Haythami mentioned it in Al-Majma (8/76) and said, "Tabarani narrated it through several chains, and the men of one of Tabarani's chains are trustworthy."