And they brought the colt to Jesus, and cast their garments on him; and he sat upon him. Mark 11:7
In the East in the time of Jesus the ass was a noble beast. In the ancient days Jair, who judged Israel, had thirty sons who rode on thirty asses (Judg. 10:4), and Abdon had forty sons and thirty grandsons who rode on seventy asses (Judg. 12:14).
The ass was the beast on which kings rode when they came in peace; only in war did they ride upon horses. The entry of Jesus was the claim to be King.
(Barclay, William., The Mind of Jesus, HarperSanFrancisco, United States of America, 1960, pg 186)