St. Cyril (375-444) was the great champion of the divine maternity.
For a long time the title “Mother of God” has been applied to Mary. Nestorius, patriarch of Constantinople, criticized it. Cyril, patriarch of Alexandria from 412, and the highest doctrinal authority in the East, took a strong stand, and, mandated by Pope Celestin, obtained the condemnation of Nestorius from the ecumenical council of Ephesus in 431.
Letter to the monks of Egypt before the Council of Ephesus to warn them against Nestorius:
Therefore, I am amazed that certain people are in any doubt as to whether the holy virgin should be called the Mother of God. For if our Lord Jesus Christ is God, how is the Virgin who bore Him not the Mother of God? The divine disciples transmitted this faith to us, even though they have not made mention of the term.
The holy fathers have taught us to think this way. Our father Athanasius, of illustrious memory, composed for us his book concerning the Holy and consubstantial Trinity. In its third discourse, he called the Holy Virgin the Mother of God from the beginning to the end.
I shall, of necessity, use his own words, which are as follows: “This, as we have often said, is the purpose and distinctive mark of Holy Scripture: It contains a twofold declaration about the Savior, in the first place, that He has always been God and is the Son—the Word, radiance, and wisdom of the Father—and in the second place, that in recent times He became man for our sake by taking flesh from the Virgin Mary, the Mother of God.” (Athanasius, Orationes contra Arianos 3:29.1)
After other matters he says again, “There have been many holy people who were even free of all sin. For Jeremiah was sanctified even from the womb, and John leaped with joy in the womb at the voice of Mary, the Mother of God.” (Contra Arianos 3:33.2) 9. This man is worthy of trust and deserves our confidence as one who would not say anything contrary to the sacred texts.
Acclamation of Mary after the Council of Ephesus:
We bless you, O holy and mysterious Trinity, who have gathered us in this church consecrated to the Mother of God.
We honor you, O Mary, Mother of God, Treasure of the Universe, Inextinguishable Flame, Crown of Virginity, Scepter of the True Faith, Indestructible Temple, Tabernacle of the One whom the World cannot Contain, and Mother and Virgin.
In your virginal womb you enclosed the immense and incomprehensible One.
Through you the Trinity is glorified and worshiped; through you the precious Cross of the Saviour is exalted and venerated throughout earth.
Through you the heavens exult with joy, the angels and archangels are glad, demons are put to flight, the demon tempter is cast out of heaven, and our fallen nature has again been assumed into Heaven.
I greet you, by whom the knowledge of truth is established on the ruins of idolatry, by whom the faithful have obtained holy baptism and have received the anointing of the oil of joy.
It is through you that all the churches of the world were founded and the nations were brought to penance.
It is through you that the Only-Begotten Son of God, the Light of the world, shone amid the nations, who were seated in darkness and the shadow of death.
It is through you that the prophets have foretold the future, through you that the apostles have foretold salvation to the nations, through you that the dead are resurrected, and it is through you that kings hold their empires.
What human voice can ever worthily celebrate the ineffable greatness of Mary? She is Mother and Virgin at the same time. Through her, peace has been restored to the world.
What peace? The peace of Our Lord Jesus Christ, whom Mary has brought forth! Amen