Excerpt from "The Wonder of the Incarnation"

"The very Son of God, older than the ages, the invisible, the incomprehensible, the incorporeal, the beginning of beginning, the light of light, the fountain of life and immortality, the image of the archetype, the immovable seal, the perfect likeness, the definition and word of the Father: he it is who comes to his own image and takes our nature for the good of our nature, and unites himself to an intelligent soul for the good of my soul, to purify like by like. He takes to himself all that is human, except for sin.

He was conceived by the Virgin Mary, who had been first prepared in soul and body by the Spirit; his coming to birth had to be treated with honour, virginity had to receive new honour. He comes forth as God, in the human nature he has taken, one being, made of two contrary elements, flesh and spirit. Spirit gave divinity, flesh received it. He who makes rich is made poor; he takes on the poverty of my flesh, that I may gain the riches of his divinity. He who is full is made empty; he is emptied for a brief space of his glory, that I may share in his fullness. What is this wealth of goodness? What is this mystery that surrounds me? I received the likeness of God, but failed to keep it. He takes on my flesh, to bring salvation to the image, immortality to the flesh. He enters into a second union with us, a union far more wonderful than the first."

From The Wonder of the Incarnation, St Gregory Nazianzen, Office of the Readings for 12/02/08