Repent, for the kingdom of heaven is near.

Matthew 4:12-16
One more thing fulfill what was said through the prophet Isiah.
When Jesus heard that John had been put in prison, he returned to Galilee. From that time on Jesus began to preach, "Repent, for the kingdom of heaven is near."
Why?
John is put in prison. Jesus, when he hears the news, travels north in what my be a tactical(戰術) withdrawal.
Jesus might feel sorrow for John was put in prison. He lost a friend in the world. But later he started his mission, it is his role on.
Matthew sees in this the fulfilment of another Old Testament prophecy.
Jesus has left his home-town of Nazareth. Now, for the whole of his ministry in Galilee.
How?
Listen to the gospel and preach the gospel. "Repent, for the kingdom of heaven is near."