The Solidarity of Jesus With God's Chosen People

By submitting Himself to John's baptism, Jesus came forward publicly to be identified with sinners, I.E., the chosen, but fallen, people of God.

The Inauguration of Jesus Into His Priestly Calling

At Jesus' baptism He is publicly called by God to bear the sins and to become obedient unto death as the kingly-priest and mediator of the new covenant.