An Excerpt from Pope St. Leo the Great
Dearly beloved brothers and sisters, unto us is born this day a Savior (Luke 2:11). Let us rejoice! It would be unlawful to be sad today, for today is Life’s Birthday; the Birthday of that Life, Which, for us dying creatures, takes away the sting of death, and brings the bright promise of eternal gladness hereafter. It would be unlawful for anyone to refuse to partake in our rejoicing. All people have an equal share in the great cause of our joy, for, since our Lord, Who is the destroyer of sin and of death, finds that all are bound under the condemnation, He is come to make all free. Rejoice, you who are holy, for you draw nearer to your crown! Rejoice, you who are sinful, for your Savior offers you pardon! Rejoice also, you gentile, for God calls you to life! For the Son of God, when the fulness of the time was come, which had been fixed by the unsearchable counsel of God, took upon Him the nature of man, that He might reconcile that nature to Him Who made it, and so the devil, the inventor of death, is met and beaten in that very flesh which hath been the field of his victory.
When our Lord entered the field of battle against the devil, He did so with a great and wonderful fairness. Being Himself the Almighty, He laid aside His uncreated Majesty to fight with our cruel enemy in our weak flesh. He brought against him the very shape, the very nature of our mortality, yet without sin (Heb. 4:15). His birth however was not a birth like other births for no other is born pure—nay, not even the little child whose life endures but a day on the earth. To His birth alone the throes of human passion had not contributed, in His alone no consequence of sin had had part. For His Mother was chosen a Virgin of the kingly lineage of David, and when she was to grow heavy with the sacred Child, her soul had already conceived Him before her body. She knew the counsel of God announced to her by the Angel, lest the unwonted events should alarm her. The future Mother of God knew what was to be wrought in her by the Holy Ghost, and that her modesty was absolutely safe.
Therefore, dearly beloved brothers and sisters, let us give thanks to God the Father, through His Son, in the Holy Ghost: Who, for His great love with which He loved us, has had mercy on us and, even when we were dead in sin, has quickened us together with Christ (Eph. 2: 4, 5), that in Him we might be a new creature, and a new work of a art. Let us then put off the old man with his deeds (Col. 3:9); and, having obtained a share in the Sonship of Christ, let us renounce the deeds of the flesh. Learn, O Christian, how great you are, who have been made a partaker of the divine nature (2 Pet. 1:4), and fall not again by corrupt conversation into the beggarly elements above which you are lifted. Remember Whose Body it is whereof you are made a member, and Who is its Head (1 Cor. 6:15). Remember that it is He That has delivered you from the power of darkness and has translated you into God’s light, and God’s kingdom (Col. 1:13).
Leo the Great, Sermon 21, from the Reading for Nocturn II of Matins for Christmas Day. Pope St. Leo the Great (c. 400 – 461) was, according to Pope Benedict XVI, “undoubtedly one of the most important in the Church’s history.” Famously, Leo so impressed Attila the Hun that the invader relented from sacking Rome.