"The Almighty and merciful God, Whose nature is goodness, Whose will is power, and Whose work is mercy, did, at the very beginning of the world, as soon as the devil's hatred had mortally poisoned us with the venom of his envy, foretell those remedies which His mercy had foreordained for our healing. He bade the serpent know that there was to be a Seed of the woman Who should yet bruise the swelling of his pestilential head; this Seed was none other than the Christ to come in the flesh, that God and Man in one Person, Who, being born of a Virgin, should, by His undefiled birth, damn the seducer of man.
"The devil rejoiced that by his fraud he had so deceived man as to make him lose the gifts of God, forfeit his privilege of eternal life, bring himself under the hard sentence of death, and find in his misery a certain comfort in the accomplice of his guilt; he rejoiced also that God, in His just anger, was changed towards man, whom He had made in such honour. But, dearly beloved brethren, that Unchangeable God, Whose Will cannot be divorced from His goodness, by His own secret counsel carried out in a mysterious way His original purpose of goodness, and man, who had been led into sin by the wicked craft of the devil, perished not to disappoint that gracious purpose of God.
"Then therefore, dearly beloved brethren, the fullness of that time came, which God had appointed for our Redemption, our Lord Jesus Christ entered this lower world, came down from His heavenly throne, and, while He left not that glory which He hath with the Father before the world was, was incarnate by a new order and a new birth new, in that He Who is Invisible among His own, was made visible among us; He Who is Incomprehensible, willed to be comprehended; He Who is before the ages, began to be in time; the Lord of all shadowed the glory of His Majesty, and took upon Him the form of a servant; the Impassible God vouchsafed to become a man subject to suffering; and the Immortal laid Himself under the laws of death." —Second Homily on the Nativity, St Leo the Great, Pope of Rome (second nocturn of Mattins)