The herald of the New

From the commentary in the Navarre New Testament Expanded Edition for tomorrow's Gospel reading, marking the Nativity of John the Baptist:

John's birth is the dividing line between the Old Testament and the New. [...] He personifies the Old and is the herald of the New. He was born of aged parents because he was to personify the Old Testament, and he was named a prophet in his mother's womb because hew was born to be the herald of the New. Before he was born, when the Virgin came, he leapt for joy in his mother's womb. That moment marked the start of his mission: he is the precursor, even before he himself can see or know is purpose. [...] He is born, and named, and his father's tongue is tied. [...] Zechariah's silence is an image of how the old prophecies were hidden, dark, closed before the preaching of Christ. Everything is made clear with the coming of the One of whom those prophecies speak (St. Augustine, Sermones, 293, 2-3).