Jesus rode a donkey into Passover. Remember that Passover was the anti-imperial Jewish festival during which the Jews celebrated their ancestors’ coming out of Egyptian Slavery. With Roman soldiers lining the streets, Jews gathered and waved palm branches, symbols of resistance to the empire. (1 Macc. 13:51) Passover was a volatile time, often marked by riots and bloodshed. When Jesus rode a donkey into this festival, it was a lampoon, like street theater at a protest. Scholars call it the anti-triumphal entry into Jerusalem.
Imagine the president riding a unicycle in the Fourth of July parade. Kings did not ride donkeys. They rode mighty war horses accompanied by an entourage of soldiers. So here is Jesus making a spectacle of violence and power, riding in on the back of an ass. (And a borrowed one at that!)
Rejoice greatly, daughter of Zion! Shout, daughter of Jerusalem! Look! Your king is coming to you: he is legitimate and victorious, humble and riding on a donkey – on a young donkey, the foal of a female donkey.