Today we venerate and celebrate the Blessed Virgin Mary, Mother of God. In 431 AD, at the Council of Ephesus, the Church dogmatically declared the orthodoxy of the Marian title 'Mother of God' (Θεοτόκος, Dei Genetrix).
«And why is this granted me, that the mother of my Lord should come to me?»
Luke 1:43 (RSVCE)
"Therefore, because the holy virgin bore in the flesh God who was united hypostatically to the flesh, for this reason we call her the Mother of God, not as if the nature of the Word had the beginning of its existence from the flesh (for 'the Word was in the beginning and the Word was God and the Word was with God' and made the ages and is co-eternal with the Father and the author of all things), but because, as we have said, she united the human hypostatically to herself and underwent a birth according to the flesh from her womb."
St. Cyril of Alexandria, Second Letter to Nestorius
℣. Holy Mother of God
℟. pray for us
