"In the sixth month the angel Gabriel was sent by God to a town in Galilee called Nazareth, to a virgin betrothed to a man named Joseph, of the House of David; and the virgin's name was Mary. He went in and said to her, 'Rejoice, you who enjoy God's favor! The Lord is with you.'
She was deeply disturbed by these words and asked herself what this greeting could mean, but the angel said to her, 'Mary, do not be afraid; you have won God's favor. Look! You are to conceive in your womb and bear a son, and you must name him Jesus. He will be great and will be called Son of the Most High. The Lord God will give him the throne of his ancestor David; he will rule over the House of Jacob for ever and his reign will have no end.'
Mary said to the angel, 'But how can this come about, since I have no knowledge of man?' The angel answered, 'The Holy Spirit will come upon you, and the power of the Most High will cover you with its shadow. And so the child will be holy and will be called Son of God. And I tell you this too: your cousin Elizabeth also in her old age, has conceived a son, and she whom people called barren is now in her sixth month, for nothing is impossible to God.'
Mary said, 'You see before you the Lord's servant, let it happen to me as you have said.' And the angel left her."
(Lk 1: 26-38)
Mary is the Mother of God, the "Theotokos"
You have just read the Bible reading of the Incarnation of the Son of God, by the power of the Holy Spirit, in the womb of a young woman from Galilee, the Virgin Mary, who had been betrothed to Joseph, a carpenter in Nazareth, "when time was fulfilled" (Ga 4: 4) gave birth to God's Word and He became man, at the same time true God and true man, taking his flesh and blood from the Virgin Mary...