On March 25 we Orthodox celebrate the Feast of the Annunciation to the Theotokos. This Feast celebrates the beginning of salvation for all creation as God becomes incarnate in the Virgin’s womb. The event is described by St. Luke in his Gospel:
In the sixth month the angel Gabriel was sent from God to a city of Galilee named Nazareth, to a virgin betrothed to a man whose name was Joseph, of the house of David; and the virgin’s name was Mary. And he came to her and said, “Hail, O favored one, the Lord is with you!” But she was greatly troubled at the saying, and considered in her mind what sort of greeting this might be. And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. He will be great, and will be called the Son of the Most High; and the Lord God will give to him the throne of his father David, and he will reign over the house of Jacob for ever; and of his kingdom there will be no end.” And Mary said to the angel, “How shall this be, since I have no husband?” And the angel said to her, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy, the Son of God. And behold, your kinswoman Elizabeth in her old age has also conceived a son; and this is the sixth month with her who was called barren. For with God nothing will be impossible.” And Mary said, “Behold, I am the handmaid of the Lord; let it be to me according to your word.” And the angel departed from her. (Luke 1:26-38)
The early Christian writer, Tertullian (d. ca 220AD) says:
“First of all, we need to show the reason why the Son of God had to be born of a Virgin. The initiator of a new birth had to be born in a new way, and Isaiah had predicted that the Lord would give a sign of this. What is that sign? ‘Behold, the virgin shall conceive in her womb and bear a Son’ (Is. 7:14). Therefore the Virgin conceived and bore Emmanuel, God-with-us.
And this is the new birth: that man is born in God when God is born in man, having assumed the flesh of the old seed, but without using this seed, and to purify the flesh after having eliminated all its ancient stains. But, as it happened, this whole new manner of birth was prefigured in the ancient wise design that depended upon a virgin. When man was created by God’s action, the earth was still virgin, not yet pressed down by man’s toil, not having been sown. We know that, from this virgin earth, God created man as a living soul.
If, then, the first Adam was introduced in this way, all the more reason that the second Adam, as the apostle said, had to come forth from a virgin earth, that is, from a body not yet violated by generation, by God’s action, so that he might become the spirit who gives life. However, lest my introduction of Adam’s name appear meaningless, why did the apostle call Christ ‘Adam’ (cf. 1 Cor. 15:45), if his humanity did not have an earthly origin? But here, too, reason comes to our aid: through a contrary operation, God recovered his image and likeness, which had been stolen by the devil.
For just as the death-creating word of the devil had penetrated Eve, who was still a virgin, analogously the life-building Word of God had to enter into a Virgin, so that he who had fallen into perdition because of a woman might be led back to salvation by means of the same sex. Eve believed the serpent; Mary believed Gabriel. The fault that Eve introduced by believing, Mary, by believing, erased.” (Luigi Gambero, Mary and the Fathers of the Church, p 67)