Musnad Ahmad 541:16

'Affan narrated to us, he said: Hammad ibn Salamah narrated to us, he said: Abu Hafs and Kulthum ibn Jabr informed us, from Abu Ghadiyah, who said: Ammar ibn Yasir was killed, so Amr ibn al-As was informed. He said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Indeed, his killer and the one who strips him [of his armor/possessions] are in the Fire." It was said to Amr: But you are fighting him! He said: He only said: "His killer and the one who strips him."