‘And he said to his servants, “This is John the Baptist. He is risen from the dead, and therefore do these powers work in him.”
Surely the only explanation for this new figure with these amazing powers was that it was John, come back from the dead. That alone explained the source of His unusual powers. This could only bode ill for Herod because of his previous treatment of John. And when a Herod was disturbed, no one knew quite what he would do.
There is a deliberate irony in that Herod is here seen as believing in the resurrection of the dead, but only as a kind of tool that God can use against him to punish him. Later Israel would have the same kind of experience through the resurrection of Jesus. Because of their unbelief His resurrection could only bring them harm as God reached out to judge them, for He was raised not only as Saviour but as judge. But there is in this belief of Herod a hint of what will actually happen to Jesus, and this is expanded on in the parallel incident in the chiasmus of the section, where we will learn that Jesus will rise from the dead (Matthew 17:23).