Matthew 21, Mark 11, Luke 19 & John 12 provide the account of Jesus triumphant entry into Jerusalem just a few days before his crucifixion.
Riding on a donkey
Mark 11:2 Jesus told his disciples “...Go your way into the village over against you: and as soon as ye be entered into it, ye shall find a colt tied, whereon never man sat; loose him, and bring him.”
Zechariah, the prophet had foretold this event. In Zechariah 9:9 “Rejoice greatly, O daughter of Zion; shout, O daughter of Jerusalem: behold, thy King cometh unto thee: he is just, and having salvation; lowly, and riding upon an ass, and upon a colt the foal of an ass.”
Why a donkey where no man had ever sat?
There are at least two explanations for this.
First, Jesus was announcing that he was the rightful king and was not entering on someone elses authority.
Second, this was not an animal that had been rode into battle or conquest. Jesus was entering Jerusalem in peace. Often, military victories were followed by generals or other leaders riding into a conquered city on the same animals used to conquer that town.