The Enchiridion by St. Augustine
Chapter 36.--The Grace of God is Clearly and Remarkably Displayed in Raising the Man Christ Jesus to the Dignity of the Son of God.
Now here the grace of God is displayed with the greatest power and clearness. For what merit had the human nature in the man Christ earned, that it should in this unparalleled way be taken up into the unity of the person of the only Son of God? What goodness of will, what goodness of desire and intention, what good works, had gone before, which made this man worthy to become one person with God? Had He been a man previously to this, and had He earned this unprecedented reward, that He should be thought worthy to become God? Assuredly nay; from the very moment that He began to be man, He was nothing else than the Son of God, the only Son of God, the Word who was made flesh, and therefore He was God so that just as each individual man unites in one person a body and a rational soul, so Christ in one person unites the Word and man. Now wherefore was this unheard of glory conferred on human nature, -- a glory which, as there was no antecedent merit, was of course wholly of grace, -- except that here those who looked at the matter soberly and honestly might behold a clear manifestation of the power of God's free grace, and might understand that they are justified from their sins by the same grace which made the man Christ Jesus free from the possibility of sin? And so the angel, when he announced to Christ's mother the coming birth, saluted her thus: |Hail, thou that art full of grace;| and shortly afterwards, |Thou hast found grace with God.| Now she was said to be full of grace, and to have found grace with God, because she was to be the mother of her Lord, nay, of the Lord of all flesh. But, speaking of Christ Himself, the evangelist John, after saying, |The Word was made flesh, and dwelt among us,| adds, |and we beheld His glory, the glory as of the only-begotten of the Father, full of grace and truth.| When he says, |The Word was made flesh,| this is |full of grace;| when he says, |the glory of the only-begotten of the Father,| this is |full of truth.| For the Truth Himself, who was the only-begotten of the Father, not by grace, but by nature, by grace took our humanity upon Him, and so united it with His own person that He Himself became also the Son of man.