While I was with Muawiya, two men came to him disputing over Ammar's head, each one saying, "I killed him."Abdullah bin Umar said, "Let one of you graciously concede it to the other, for I heard the Messenger of Allah ﷺ say, 'The transgressing party will kill him.'"Muawiya asked, "Then why are you here with us?"He replied, "My father once complained about me to the Messenger of Allah ﷺ, who said, 'Obey your father as long as he lives, and do not disobey him.' So I am with you, but I am not fighting."
بينما أنا عند معاوية، إذ جاءه رجلان يختصمان في رأس عمار، يقول كل واحد منهما، أنا قتلته، فقال عبد الله بن عمرو: ليطب به أحدكما نفسا لصاحبه، فإني سمعت رسول الله ﷺ يقول: تقتله الفئة الباغية، قال معاوية: فما بالك معنا؟ قال: إن أبي شكاني إلى رسول الله ﷺ فقال: أطع أباك ما دام حيا، ولا تعصه، فأنا معكم ولست أقاتل.
Ahmad (6538), Ibn Abu Shayba in his Musannaf (39000), and Nasai in Khasais Ali (164) all narrated it through the route of Yazid bin Harun, who said, Awwam bin Hawshab informed us, Aswad bin Masud narrated to me, from Hanzala bin Khuwaylid, and he mentioned it. Its isnad is sahih.