In the Announcement to Zechariah, the unborn John the Baptist is described as follows:
"Your wife Elizabeth is to bear you a son and you shall name him John.
14 He will be your joy and delight and many will rejoice at his birth,
15 for he will be great in the sight of the Lord; he must drink no wine, no strong drink; even from his mother's womb he will be filled with the Holy Spirit,
16 and he will bring back many of the Israelites to the Lord their God.
17 With the spirit and power of Elijah, he will go before him to reconcile fathers to their children and the disobedient to the good sense of the upright, preparing for the Lord a people fit for him."
(Lk 1:13-17)
Zechariah is told that John "will be great in the sight of the Lord" (Lk 1:15).
Mary is told that Jesus, for his part, "will be great" (Lk 1:32), without a term of comparison or limit. The epithet "great" is reserved for God in the Old Testament.
Zechariah is told that John "will be filled with the Holy Spirit" (Lk 1:15). His conception is the fruit of the meeting of Zechariah and Elizabeth (Lk 1:23-24).
Mary is told that Jesus will be conceived by the Holy Spirit: "The Holy Spirit will come upon you, and the power of the Most High will cover you with its shadow" (Lk 1:35). Here, God comes down: It is a new creation.
In his canticle, Zechariah expresses the truth that John would become "Prophet of the Most High" (Lk 1:76).
Mary is told that Jesus would "be called Son of the Most High" (Lk 1:32), "Son of God" (Lk 1:35).
John the Baptist's mission is to "bring back many of the Israelites to the Lord their God" (Lk 1:16).
Jesus' mission is to be the messianic king of the new people of God (Lk 1:32-33), his own people.
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Aristide Serra
Excerpt from A. Serra "Bibbia", Nuovo dizionario di mariologia,a cura di .S. di Fiores e S. Meo, ed. San Paolo, Milano 1986