Musnad Ahmad 1007:91

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Abdullah ibn Abi Bakr narrated to me that he was told by Abu Qatadah, he said: My father, and Ibn Ishaq narrated to me, from Yahya ibn Sa'id, from Nafi' al-Aqra' Abu Muhammad, the freed slave of Banu Ghifar, from Abu Qatadah, he said: Abu Qatadah said: I saw two men fighting, a Muslim and a polytheist. A man from the polytheists wanted to assist his polytheist companion against the Muslim, so I came to him and struck his hand and severed it. He embraced me with his other hand, and by Allah, he did not release me until I felt the scent of death. Had it not been that the blood drained him, he would have killed me. He fell, so I struck him and killed him, and the fighting distracted me from him. A man from the people of Makkah passed by him and took his spoils. When we finished and the war laid down its burdens, the Messenger of Allah (ﷺ) said: "Whoever kills a person killed in battle, his spoils belong to him." I said: "O Messenger of Allah, I killed a person who had spoils, but the fighting distracted me from him, so I do not know who took his spoils." A man from the people of Makkah said: "He has spoken the truth, O Messenger of Allah. I took his spoils, so compensate him on my behalf for his spoils." Abu Bakr said: "You intend to take from a lion of the lions of Allah, who fights for the sake of Allah, the Mighty and Majestic, and share his spoils with him? Give him back the spoils of the one he killed." The Messenger of Allah (ﷺ) said: "He has spoken the truth, so give him back the spoils of the one he killed." Abu Qatadah said: So I took it from him and sold it, and with its price, I bought a garden in Madinah, and it was the first property I acquired.