'Auf bin Malik (RAA) narrated, "The Messenger of Allah (ﷺ) judged that the belongings taken from the (non-Muslim enemy) killed soldier in a war, are to be given to the one who killed him.' Related by Abu Dawud. Muslim reported it as part of a long hadith.
English reference: Book 11, Hadith 1319
Arabic reference: Book 11, Hadith 1292