The Old Testament has lots of prophecies about the Christ, the Messiah who would deliver God's chosen people. Over the centuries, people had a lot of ideas about the Messiah. By Jesus' time, people hoped the Messiah would be a military leader, to throw out the Romans and restore them to their former glory as a nation.
A few weeks ago, in the Gospel with Jesus walking on the water, the Apostles figure out why Jesus knows what he knows and what that means about who Jesus is. In last Sunday's Gospel, Peter comes out and says it, calling Jesus "the Christ, the son of God."
And right after Peter's moment of awesome, Jesus tells the Apostles not to tell anybody that he is the Christ, the Messiah. It's a secret.
Why? Is the Messiah preparing a surprise attack on the Romans? Or is this some kind of covert operation with spies and assassinations?
As we'll see tomorrow, the answer (and it's not what we might expect) is in this Sunday's Gospel - and in Jeremiah.