Musnad Ahmad 788:117

Al-Hakam ibn Nafi’ Abu al-Yaman narrated to us, Isma’il ibn ‘Ayyash narrated to us, from ‘Abd al-‘Aziz ibn ‘Ubayd Allah, from Abu Burdah ibn Abi Musa al-Ash’ari, from his father, from the Prophet (peace and blessings of Allah be upon him), that he used to grant extra shares of spoils (nafal) in his military expeditions.