It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) (on the occasion of the Battle of Khaybar) allotted two shares for the horse and one share for the rider.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 6297