"I was completely amazed that certain people should be in any doubt as to whether the holy virgin ought to be called the Mother of God or not. For if our Lord Jesus Christ is God, then how is the holy virgin who bore him not the Mother of God? The divine disciples handed on this faith to us even if they did not make mention of the term. We have been taught to think this way by the holy Fathers. Our Father Athanasius, of illustrious memory, was an ornament to the throne of the church of Alexandria throughout forty six years in all. He opposed an unconquered and apostolic wisdom to the sophistries of the evil heretics, and refreshed the whole world with his own writings as if they were some most fragrant balsam. His orthodoxy and godliness in teaching are confessed by all, and he composed a book for us concerning the holy and consubstantial trinity where, throughout the third discourse, he calls the holy virgin the Mother of God. I will make use of his own sayings and the exact words are these: 'This, then, is the purpose and essential meaning of the divine scripture, as we have said many times, that it contains a two-fold statement about the Savior; firstly that he is eternally God, and that he is the Son being the Word, the Radiance, and the Wisdom of the Father, and secondly that later for our sake he took flesh from the virgin Mary the Mother of God and so became man.' And again, further on, he says: 'But there have been many holy men who were even pure of all sin. Jeremiah was sanctified even from the womb, and John still inside his mother leaped for joy at the sound of the voice of Mary the Mother of God.' This man is trustworthy and we ought to rely upon him as someone who would never say anything that was not in accordance with the sacred text. For how could such a brilliant and famous man, held in such reverence by everybody at the holy and great Synod itself (I mean that which formerly gathered together in Nicaea) be mistaken as to the truth? At the time he did not occupy the episcopal throne, but was still only a cleric. Nonetheless because of his shrewdness, his purity of life, and his sharp and incomparably penetrating mind, he was taken along on that occasion by bishop Alexander of blessed memory, and he was to the old man like a son to a father, guiding him in everything useful and admirably showing him the way in all he did."
-Cyril of Alexandria