As for Isḥāq ibn Banān, he has a biography in "Tārīkh Baghdād" (6/390-391) and it is narrated from al-Dāraqutnī that he is trustworthy. Thus, the isnād is authentic, and all praise is due to Allāh.

By the One in Whose hand is my soul, I see his flesh between your teeth. Meaning the flesh of the one they backbit. It was recorded by al-Kharāʾiṭī in "Masāwī al-Akhlāq" (186) and al-Ḍiyāʾ al-Maqdisī in "al-Mukhtārah" (2/33/2) through various chains from Abū Badr ʿAbbād ibn al-Walīd al-Ghubarī: Ḥibbān ibn Hilāl narrated to us, Ḥammād ibn Salamah narrated to us from Thābit al-Bunānī from Anas ibn Mālik who said: "The Arabs used to serve each other during travels, and there was a man with Abū Bakr and ʿUmar who served them. They both fell asleep, and when they awoke, he had not prepared food for them. One of them said to his companion: This man sleeps like your Prophet ﷺ (in another narration: like your household). So they woke him and said: Go to the Messenger of Allāh ﷺ and tell him: Abū Bakr and ʿUmar send you greetings of peace, and they are asking for your condiment. He said: Convey my greetings of peace to them, and inform them that they have already had their condiment! They were alarmed, so they went to the Prophet ﷺ and said: O Messenger of Allāh! We sent to you asking for your condiment, and you said: You have already had it. With what did we have our condiment? He said: With the flesh of your brother, by the One in Whose hand is my soul (and he mentioned it). They said: Seek forgiveness for us, he said: Let him seek forgiveness for you." I say: This isnād is authentic, all its narrators are trustworthy, the men of Muslim, except for Abū Badr al-Ghubarī, about whom Abū Ḥātim and followed by al-Ḥāfiẓ said: "Truthful." Ibn Ḥibbān mentioned him in "al-Thiqāt." A group of trustworthy ḥadīth scholars narrated from him, and he was corroborated, as al-Ḍiyāʾ said afterwards: "ʿAffān ibn Muslim also narrated it from Ḥammād ibn Salamah from Thābit from ʿAbd al-Raḥmān ibn."