Musannaf Ibn Abi Shayba 38:119

Ali ibn Hafs narrated to us, from Abu Ma'shar, from Muhammad ibn 'Umarah ibn Khuzaymah ibn Thabit, who said: My grandfather continued to withhold his weapon on the day of Siffin and on the day of the Camel, until Ammar was killed. When he was killed, he drew his sword and said: I heard the Messenger of Allah, may Allah bless him and grant him peace, say: "The rebellious faction will kill Ammar." So he fought until he was killed.