When Ammar bin Yasir was killed, Amr bin Hazm went in to see Amr bin As and said, "Ammar has been killed, and the Messenger of Allah ﷺ said, 'The transgressing party will kill him.'"Amr bin As got up alarmed and hurried back until he went in to Muawiya.Muawiya asked him, "What is the matter with you?"He replied, "Ammar has been killed."Muawiya said, "Ammar has been killed, so what?"Amr said, "I heard the Messenger of Allah ﷺ say, 'The transgressing party will kill him.'"Muawiya said to him, "You have slipped in your own urine. Did we kill him? Ali and his companions are the ones who killed him. They brought him and threw him between our spears," or he said, "between our swords."
لما قتل عمار بن ياسر دخل عمرو بن حزم على عمرو بن العاص، فقال: قتل عمار، وقد قال رسول الله ﷺ: تقتله الفئة الباغية، فقام عمرو بن العاص فزعا يرجع حتى دخل على معاوية، فقال له معاوية: ما شأنك؟ قال: قتل عمار، فقال معاوية: قد قتل عمار، فماذا؟ قال عمرو: سمعت رسول الله ﷺ يقول: تقتله الفئة الباغية، فقال له معاوية: دحضت في بولك، أو نحن قتلناه؟ إنما قتله علي وأصحابه، جاءوا به حتى ألقوه بين رماحنا أو قال: بين سيوفنا.
Ahmad (17778) and Abu Yaala (7175) narrated it, and Hakim graded it sahih (2/155-156), all of them through the route of Abdul-Razzaq (it is in his Musannaf, 20427), Muammar narrated to us, from Ibn Tawus (whose name was Abdullah), from Abu Bakr bin Muhammad bin Amr bin Hazm, from his father, who said, then he mentioned it. Its isnad is sahih.His saying "yarjiu" means he says, "Indeed, we belong to Allah, and indeed to Him we will return" [Baqarah 2:156]. And his saying "dahadat" means he stumbled and erred in understanding.It is narrated from Abu Ghadiya that he said, Ammar bin Yasir was killed, and Amr bin As was informed. He said, I heard the Messenger of Allah ﷺ say, "Indeed, his killer and the one who takes his belongings are in the Fire." It was said to Amr, "But here you are fighting him." He said, "He only said, 'his killer and the one who takes his belongings.'"Ahmad (17776) and Ibn Saad in his Tabaqat (3/260-261) both narrated it from Affan bin Muslim, Hammad bin Salama narrated to us, Abu Ahwas and Kulthum bin Jabr informed us, from Abu Ghadiya (whose name was Yasar bin Sabi, and he was a companion), who said, then he mentioned it.This is how Ahmad presented it, in brief. As for Ibn Saad, he presented it with a longer account, in which it states, from Abu Ghadiya, he said, I heard Ammar bin Yasir speaking against Uthman and cursing him in Madinah. He said, so I threatened him with killing. I said, "If Allah gives me power over you, I will surely do it." Then, on the day of Siffin, Ammar began charging at the people. It was said, "This is Ammar." I saw a gap between the lungs and the legs. He said, so I charged at him and struck him in the knee. He said, so he fell, and I killed him. It was said, "You have killed Ammar bin Yasir." Amr bin As was informed, and he said, I heard the Messenger of Allah ﷺ say, "Indeed, his killer and the one who takes his belongings are in the Fire." It was said to Amr bin As, "But here you are fighting him." He said, "He only said, 'his killer and the one who takes his belongings.'"Abu Ahwas's name was Awf bin Malik bin Nadla. In the printed edition of the Musnad it says "Abu Hafd," but the correction comes from Ithaf Mahra (15974).This hadith, despite the soundness of its isnad, is shadh, contradicting the sahih and well-established hadiths, for it is the rebellious group as a whole that killed Ammar, not the killer alone. Perhaps Amr bin As said, "Indeed, his killer and the one who takes his belongings are in the Fire," as his own ijtihad, and some narrators then attributed it to the Prophet. Allah knows best what is correct.As for his statement that "Ammar bin Yasir was speaking against Uthman and cursing him in Madinah," it is not mentioned in the accounts of Ammar bin Yasir's life in the books of biographies or elsewhere that he used to curse Uthman. Perhaps this was simply Abu Ghadiya's own understanding, since he was among the partisans of Uthman, while Ammar was among the partisans of Ali bin Abu Talib, may Allah be pleased with all of them. It is possible that Ammar said something critical of Uthman, and Abu Ghadiya took it to be cursing and abuse. Allah knows best what is correct.As for Abu Ghadiya, he is the one who killed him, as will appear in the following hadith.