Musannaf Ibn Abi Shayba 28:563

Waki’ narrated to us, he said: ‘Ikrimah ibn ‘Ammar narrated to us, from Iyas ibn Salamah ibn al-Akwa’, from his father, he said: I engaged in a duel with a man and killed him. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Who killed this?" Ibn al-Akwa’ said: "I did." He said to him: "[Take] his spoils."