Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said: In the Battle of Mu'tah some of the Muslims were struck down, and the Muslims took some of the belongings of the polytheists as spoils. Among what they took was a ring, which a man brought to the Messenger of Allah (peace and blessings be upon him). He said: I killed its owner that day. So the Messenger of Allah (peace and blessings be upon him) gave it to him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12775