John 12:15
“Rejoice greatly, daughter of Zion.”
Because all their kings had for the most part been an unjust and covetous kind of men, and had given them over to their enemies, and had perverted the people, and made them subject to their foes; “Be of good courage,” It says, “this is not such an one, but meek and gentle”; as is shown by the ass, for He entered not with an army in His train, but having an ass alone.
Source: Homilies on the Gospel of John (New Advent)