In Nativitate S. Ioannis Baptistae: "To receive a name from God is one of the honours of the Saints"

Luke 1:57-69
Elisabeth's fullness of time came that she should deliver, and she brought forth a son. And her neighbours and her cousins heard how the Lord had showed great mercy upon her, and they rejoiced with her. And so on.

From the Sermons of St. Augustine, Bishop of Hippo.
20th on the Saints.
Outside the most holy Birthday of the Lord, we find celebrated in the Gospel the birth of only one other, namely, that of the blessed Baptist, John. As regardeth all others among God's holy and chosen ones we know that that day is observed whereon, with their work finished, and the world conquered and finally trampled down, they were born from this into a better life, even one of everlasting blessedness. In others is honoured the crowning of the struggle on their last day of dying life, but in John is honoured the first day; in him the very beginning is found hallowed. And the reason of this is, without doubt, because he was sent from God to bear witness to the coming of the Light, lest when It came It might take the darkness by surprise, and the darkness might not comprehend It. Now, John was a figure of the Old Testament, and showed in his own person a typical embodiment of the Law; and therefore John heralded beforehand the coming of the Saviour, even as the Law was our schoolmaster to bring us to the grace of Christ. Gal. iii. 24.

But as touching this, that he prophesied while yet in the hidden depths of his mother's womb, and while himself lightless bore testimony to the truth, we are to understand it as a figure how that while himself wrapped round with the veil and carnal ordinances of the letter, he by the spirit preached unto the world a Redeemer, and testified that Jesus is our Lord even while for himself, working under the law, the birth of the new dispensation was still in the womb of the future, and not come to day. The Jews were estranged from the womb, that is from the Law, that womb heavy with the Christ That was to be; they went astray from the belly, speaking lies, Ps. lvii. 4; and therefore John came for a witness, to bear witness of the Light, that all men through him might believe. John i. 7.

But as for this, that when John had heard in the prison the works of Christ, he sent two of his disciples Matth. xi. 2; this is the Law sending to the Gospel. For John here was a figure of the Law, imprisoned in ignorance, lying in the dark, and in a hidden place, and he was fettered through Jewish misunderstanding within the bonds of the letter. But of him was it said, as is written in the Blessed Evangelist He was a burning and a shining light that is to say, that, when the whole world was wrapt in the night of ignorance, this Saint was kindled by the fire of the Holy Ghost, to show before men the light of salvation, and at the hour of the thickest darkness of sin, appeared like a bright morning star to herald the rising of that Sun so right gloriously radiant, the Son of righteousness, Christ our Lord. And this is why John said of himself: I am the voice of one crying in the wilderness, Make straight the way of the Lord. John i. 15.

Homily by St. Ambrose, Bishop of Milan.
Bk. ii. Comm. on Luke i.
Elizabeth's full time came that she should be delivered, and she brought forth a son. And her neighbours rejoiced with her. The birth of a Saint is a joy for many, for it is a good to all. Righteousness is an help to all, and therefore when a righteous man is born it is an heralding of his life, which is still to come, that the helpful excellency of his future should be hailed by the, as it were, prophetic joy of the neighbours. It is well that we should be told concerning the prophet, while he was yet in the womb, that we may know how that Mary was there; but we hear nothing of his childhood, because,we know that it was safe and strong through the nearness of the Lord, Himself then in that womb which was free from the sorrows of pregnancy. And therefore we read in the Gospel nothing touching him save his coming, the annunciation thereof to his father, the leap which he gave in the womb, and his crying in the wilderness.

It was not for him to feel childishness, who beyond all use of nature or of his age, when as yet he lay in his mother's womb, leapt at once unto the measure of the stature of the fullness of Christ. Eph. iv. 13. It is strange how that the Holy Evangelist hath judged meet to tell us that they thought to call the child Zacharias, after the name of his father, that thou mayest notice that the mother would have none of the names whereby their kindred were called, but only that name which the Holy Ghost had dictated, and which the Angel had told before unto Zacharias. The dumb man had certainly not been able to tell his wife by what name to call the child, and Elizabeth must needs have learnt by revelation what she could not have heard from her husband.

His name is John; that is, it is not for us to choose a name now for him to whom God hath given a name already. He hath a name, which we know, but it is not one of our choosing. To receive a name from God is one of the honours of the Saints. Thus was it that Jacob's name was no more called Jacob but Israel, because he saw God face to face. Gen. xxxii. 28. Thus was it that our Lord Jesus was named before He was born, with a name not given by an Angel, but by the Father. Thou seest that Angels tell that which they have been bidden to tell, not matters of their own choosing. Nor oughtest thou to wonder that Elizabeth named a name which she had not heard, since it had been revealed to her by the same Holy Ghost Who had commanded the Angel to tell it