"HELP!"
It's not uncommon for kids to get into a place in which they need the help of their parents and they use the phrase "I need help."
All of these are fairly simple tasks for the parent, however, the kid has reached the end of their rope and just say "Help!"
Something similar to that is happening in Matthew 21:9.
MATTHEW 21:9
Jesus is entering Jerusalem on a donkey and Israel is so out of sorts with their situation (for a variety of reasons) that all they can say is "Help!" It comes out like this in Matthew 21:9:
“[Save us!] Son of David!”
Israel is at the end of their rope.
They recognize that their own efforts for political reform, national reform, religious reform have all turned at a loss.
So they cry out to Jesus for help.
JESUS IS HERE TO HELP
For Israel, this "Save us!" cry (or "Hosanna" as the text more literally says), was an articulation of a deep personal, social, political desire for reform and to be brought back to God.
Through the events that follow, Jesus will do exactly that.
He will create a way to - through the cross - for people to draw near to God.
And the cross still stands.
Jesus is still the way that our:
...can be saved.
This Holy Week we recognize afresh that we need saving.
And so we join the cry of the crowd from 2,000 years ago.
"[Save us!] son of David!"