From Bishop Robert Barron
Friends, on this feast of the Baptism of the Lord, let us meditate on John the Baptist. Young John, the son of the priest Zechariah, grew up in and around the Temple, acquainted with its rituals. And he sensed that the true Messiah was on the horizon. And so he went away from the old Temple, but he continued to act as a priest of a new Temple.
He was baptizing people. Why this ritual? Well, in the Jerusalem Temple, a pilgrim would cleanse himself in a mikvah, a ritual bath, before he entered to make sacrifice. John was acting as a priest, and the River Jordan was his mikvah. But what—or, better, who—was the new Temple? Jesus who came from Nazareth of Galilee and was baptized by John. The heavens were torn open and the Spirit, like a dove, descended on him.
This is Temple talk. When the high priest entered into the holy of holies, he was entering into the heavenly realm. The holy of holies was the place where the “heavens were torn open” and a humble human being could enter. So the point is that Jesus is himself the new holy of holies.