The preferred manner of standing at Arafah (riding or walking).
Chapter on the Description of Hajj
Al-Mughni
Book of Hajj
Primary text
It is better to stand while riding a mount, as the Prophet, peace be upon him, did, as this aids in supplication. Ahmad affirmed this when questioned, noting the Prophet stood on his riding animal.
Supporting text
It is also suggested that standing on foot is superior because it is easier on the animal. A third position allows for equality between the two.