Abu Dawud Book 13, Hadith Number 3009.

Narated By Mujammi’ ibn Jariyah al-Ansari, : Khaybar was divided among the people of al-Hudaybiyyah. The Apostle of Allah (PBUH) divided it into eighteen portions. The army contained one thousand and five hundred people. There were three hundred horsemen among them. He gave double share to the horsemen, and a single to the footmen.