Hani, the mawla of Amr, narrates: I was with Sayyiduna Mu'awiyah (may Allah be pleased with him) and Sayyiduna Amr bin al-As (may Allah be pleased with him) at Siffin. That day I looked over the slain, and I found Sayyiduna Ammar bin Yasir (may Allah be pleased with him) among the killed. We went to Sayyiduna Amr bin al-As (may Allah be pleased with him), and I said: What have you heard the Prophet (peace and blessings be upon him) say about Sayyiduna Ammar (may Allah be pleased with him)? He replied: I heard the Prophet (peace and blessings be upon him) say to Ammar: "A rebellious group will kill you." The narrator says: I said: Then Sayyiduna Ammar (may Allah be pleased with him) has been killed by you people! Sayyiduna Amr (may Allah be pleased with him) did not accept this, and he said: Go and show him to me! So I went and stood over Sayyiduna Ammar (may Allah be pleased with him), and I asked: What do you say about him? He replied: His own companions caused him to be killed.
Al-Tabarani recorded it as a lengthy narration, and he also recorded it in a shortened form. The narrators of the shortened narration are the narrators of the Sahih, except Ziyad, the mawla of Sayyiduna Amr (may Allah be pleased with him), and Ibn Hibban declared him thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15622