God once again reveals Jesus’ identity as his son and annoints him for mission like he did at his baptism. This one phrase, repeated, confirms Jesus as the fulfillment of the prophecies in the Old Testament and points the disciples to the truth of the new covenant: God once again dwells with us. 

The transfiguration isn’t for the mountaintop alone- it informs our identity and calling as followers of Jesus and sends us back into the world with the foundation of a Jesus-shaped church: God with us.