See the notes at Matthew. 21:1-16.

He went before - Joyfully to anticipate his death, say some. Perhaps it means that he walked at the head of his disciples; and that he and his disciples kept on the road before other companies who were then also on their way to Jerusalem, in order to be present at the feast.

And when he had thus spoken, (f) he went before, ascending up to Jerusalem.
(f) The disciples were staggered and stopped by what Christ said, but Christ goes on boldly even though death was before his eyes.

And when he had thus spoken,.... When he had delivered the above parable, in order to remove the prejudices of his disciples, and the multitude, concerning a temporal kingdom, and to give them true notions of his own kingdom, and the case of the Jewish nation:
he went before; his disciples: he was the foremost of them in the journey; he proceeded at the head of them, with great cheerfulness and eagerness:
ascending up to Jerusalem; through the lower lands of Judea, to the city of Jerusalem, which was built on higher ground; where he was to eat his last passover, and suffer, and die, in the room, and stead, of his people; and this shows how willing, and greatly desirous he was to finish the work of redemption he came about.

Christ has dominion over all creatures, and may use them as he pleases. He has all men's hearts both under his eye and in his hand. Christ's triumphs, and his disciples' joyful praises, vex proud Pharisees, who are enemies to him and to his kingdom. But Christ, as he despises the contempt of the proud, so he accepts the praises of the humble. Pharisees would silence the praises of Christ, but they cannot; for as God can out of stones raise up children unto Abraham, and turn the stony heart to himself, so he can bring praise out of the mouths of children. And what will be the feelings of men when the Lord returns in glory to judge the world!

Going up to Jerusalem. The ascent begins at Jericho, and about 3,000 feet has to be climbed before the city is reached. The account of the royal entrance into Jerusalem is given in Matthew. 21:1-16; Mark 11:1-11, and John 12:12-19. See the notes on Matthew.
At the descent of the mount of Olives. Where the city and temple burst into view.