Musnad Ahmad 27:963

'Affan narrated to us, Sulaym ibn Akhdar narrated to us, 'Ubayd Allah narrated to me, from Nafi', from 'Abd Allah ibn 'Umar: "That the Prophet, peace and blessings of Allah be upon him, allotted in the spoils of war two shares for the horse, and one share for the man."