Mary is the mother of Jesus Christ, who is God and man. She is therefore the Mother of God. This is a dogma of the Faith accepted as such from the earliest times, as is evident from countless expressions of the Fathers. It does not mean, of course, that Mary generated the Godhead. It simply means that she is the mother of a Person who is God. This is her fundamental dignity, and the origin and justification of the honor which Catholics pay to her.
Mary is called the Mother of Jesus:
Jn. 2:1 – On the third day there was a marriage at Cana in Galilee, and the mother of Jesus was there…
Mary is called the Mother of my Lord:
Lk. 1:43 – And why is this granted me, that the mother of my Lord should come to me?
Lk. 1:28-33 – And he came to her and said, “Hail, full of grace, the Lord is with you!” 29 But she was greatly troubled at the saying, and considered in her mind what sort of greeting this might be. 30 And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. 31 And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. 32 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, 33 and he will reign over the house of Jacob for ever; and of his kingdom there will be no end.”
The motherhood of God is included in the words of St. Luke:
Mary’s true motherhood is clearly foretold by the prophet Isaiah:
Is. 7:14 – Therefore the Lord himself will give you a sign. Behold, a young woman shall conceive and bear a son, and shall call his name Immanuel.
The woman who bore the Son of God is the Progenitress of God, or the Mother of God.
Mt. 1:23 – Behold, a virgin shall conceive and bear a son, and his name shall be called Emmanuel (which means, God with us).
Gal. 4:4-5 – But when the time had fully come, God sent forth his Son, born of woman, born under the law, 5 to redeem those who were under the law, so that we might receive adoption as sons.
St. Ignatius of Antioch [AD 107] – For our God, Jesus Christ, was conceived by Mary in accord with God’s plan: of the seed of David, it is true, but also of the Holy Spirit. (Letter to the Ephesians 18, 2).
St. Irenæus of Lyon [AD 180-199] – The Word Himself, born of Mary who was still a virgin, rightly received in birth the recapitulation of Adam, thereby recapitulating Adam in Himself. (Against Heresies 3, 21, 10).
The Virgin Mary, …being obedient to His word, received from an angel the glad tidings that she would bear God. (Against Heresies, 5, 19,1).
St. Ephraim [AD 306-373] –
In the womb of Mary the Infant was formed,
Who from eternity is equal to the Father.
He imparted to us His greatness,
And took on our infirmity.
He became mortal like us and joined his life to ours,
So that we might die no more.
(Songs of Praise 1, 12).
Alexander of Alexandria [AD 324] – After this, we acknowledge the resurrection of the dead, of which Jesus Christ our Lord became the firstling; who bore a body not in appearance but in truth, derived from Mary the Mother of God (Letters 12).