A sermon of S.Leo the Great
"Dearly beloved : Unto us is born this day a Saviour. Therefore let us rejoice. Sadness should find no place amongst those who keep the Birthday of Life. For as of this day Life came unto us dying creatures, to take away the sting of death, and to bring the bright promise of joy eternal. And no one is excluded from sharing in this our gladness. For all mankind hath one and the same cause thereof, to wit, that our Lord, the Destroyer of sin and death, because he findeth no one free from condemnation, is come to set everyone free. Rejoice, O saint, for thou drawest nearer thy crown! Rejoice, O sinner, for thy Saviour offereth thee pardon! Rejoice, O Jew, for Messias is come. Rejoice, O Gentile, for God calleth thee to life! Now is come the fulness of time, fixed by the unsearchable counsel of God, when the Son of God took upon him the nature of man, that he might reconcile it to its Maker. Now is come the time when the devil, the inventor of death, is met and beaten in that very flesh which hath been the field of his victory.
When the Almighty Lord entered this field of battle against the devil, he did so in great and wondrous fairness. For against our cruel enemy he opposed not the armament of his uncreate Majesty, but the lowliness of our flesh. He brought against him the very shape and the very nature of our mortality, with this difference only, that he was without sin. For his birth is not like that of the ordinary run of men, of whom there is the saying : No one is clean from stain, not even the day-old babe. In this birth alone no desires of the flesh had place. In this birth alone no consequence of sin had part. A Virgin of the kingly lineage of David was chosen to be the Mother who grew heavy with the sacred Child. She was chosen to conceive this divine and human offspring in her body because already she had conceived him in her soul. And that the unwonted events ordained by the counsel of God might cause her no alarm, she was taught them beforehand when the Angel announced that what was to be wrought in her was of the Holy Ghost, and that to become the Mother of God was not to forego her virgin modesty.
Wherefore, dearly beloved, let us give thanks to God the Father, through his Son, in the Holy Ghost : who for his great love, wherewith he loved us, hath had mercy on us ; and even when we were dead in sins, hath quickened us together with Christ, that in him we might be a new creature, and a new workmanship. Let us then put off the old man with his deeds. And, having obtained a share in the Sonship of Christ, let us renounce the deeds of the flesh. Acknowledge, O Christian, thine own dignity, who hast been made partaker of the divine nature, and change not back my misdoing into thy former baseness. Bethink thee whose Body it is whereof thou art made a member, and who is its Head. Be mindful that he hath delivered us from the power of darkness, and translated us into God's light and God's kingdom."