In this week's reading, the people recognize Jesus as the king as he comes riding in on a donkey (look at Zechariah 9:9--go ahead and read the rest of the chapter as well to help understand what the people were expecting from the king and the Lord). Crowds gather, they throw their cloaks on the road (as had been done for King Jehu, 2 Kings 9:13).
Large numbers of followers begin to shout loudly their thanks to God for giving them this king.
Not everyone is pleased.
When some in the crowd tried to get him to get his disciples to quiet down, he responded "Even if they were silent, the stones would cry out." He's reminding them what Habakkuk had said about the powerful who try to protect themselves from debtors (Habakkuk 2:6-11).
Now, another way to look at this passage: I wouldn't have noticed the absence of palms in Luke's version if Allen & Williamson had not pointed it out to me in their Preaching the Gospels without Blaming the Jews:
Luke's omission of these branches is significant. Branches recollect 1 Maccabees 13:49-53. For three centuries Palestine had been under foreign rule. In 141 BCE, Jewish rebels defeated the Syrian oppressors. When the Jewish victors recaptured the temple, they waved branches. The branches became a symbol of Jewish independence, By omitting them, Luke signals that the church is not a revolutionary movement and encourages his community to live within Roman rule even while criticizing that oppression and recognizing that God will judge Rome ...