Abu Dawud Book 13, Hadith Number 2945.

Narated By Abdullah ibn Umar : Zayd ibn Aslam said: Abdullah ibn Umar entered upon Mu’awiyah. He asked: (Tell me) your need, AbuAbdurRahman. He replied: Give (the spoils) to those who were set free, for I saw the first thing the Apostle of Allah (PBUH) did when anything came to him was to give something to those who had been set free.