Musnad Ahmad 32:191

Yahya ibn Sa'id narrated to us, from Hammad—meaning ibn Salamah—, Ishaq ibn Abdullah narrated to us, from Anas ibn Malik, that the Messenger of Allah (ﷺ) said on the day of Hunayn: "Whoever kills a disbeliever, for him is his spoils." He said: So Abu Talhah killed twenty.