St Leo the great (461 AD) Christmas homily
In the Name + of the Father and of the Son and of the Holy Spirit. [Amen]
Our Savior, dearly-beloved, is born today: let us be glad. For there is no proper place for sadness when we are keeping the birthday of Life, which destroys the fear of mortality and brings to us the joy of promised eternity. No one is kept from sharing in this happiness. There is for all one common measure of joy, because as our Lord, the Destroyer of sin and death, finds no one free of blame so does He come to free us all. Let the saint exult in that he draws near to victory. Let the sinner be glad in that he is invited to pardon. Let the gentile take courage in that he is called to life.
For the Son of God in the fulness of time, as the good and gracious Will of God determined, has taken for Himself the nature of man, thereby to reconcile man to his Creator: in order that the inventor of death, that is, the devil, might be conquered by means of that very nature which he had conquered. And in this conflict, which the Lord has undertaken for us, the fight is fought on great and wondrous principles of fairness; for the Almighty Lord engages the battle with His savage foe, not in His own majesty, but in our humility, opposing him with the same form and the same nature with which He shares our mortality, though He is free from all sin. For truly foreign to His Holy Nativity is that guilt and shame and sin which otherwise stains our human conception and birth.
Nothing therefore of the lust of the flesh has passed into His spotless and peerless Nativity; nothing of the law of sin has entered. A royal Virgin of the stem of David is chosen, to be impregnated with the sacred Seed of the Word, and to conceive the Divinely-human Offspring--in her ears first, in heart and mind, and also in body. And lest, in her ignorance of the heavenly counsel, she should tremble at such a great and mighty wonder, she learns from converse with the angel that what is conceived in her is of the Holy Spirit.
Nor does St. Mary believe it a loss of honor that she thus becomes the Mother of God. For why should she be in despair over the novelty of such conception, to whom the power of the most High has promised to effect it. Her faith is also confirmed by the demonstration of an earlier miracle, that barren Elizabeth has received unexpected fertility (in conceiving St. John the Baptist): so there may be no doubt, that He who has given conception to the barren, has also given it even to the Virgin.
Therefore the Word of God, Who is God Himself, the very Son of God, Who was "in the beginning with God," through Whom "all things were made," and "without" Whom "was nothing made," with the purpose of delivering man from eternal death, became Man. Lowering Himself to assume our humility, yet without decreasing in His own majesty, He remained Who and What He was, while He also assumed what He was not. So did He unite within Himself the true form of a slave to that form in which He is equal to God the Father, and He joined both natures together in such a way that the lower should not be swallowed up in its exaltation nor the higher impaired by its new association.
Thus, without destroying His Divinity, nor shattering our humanity (which He took for His own), these came together in one Person: majesty took on humility, strength weakness, eternity mortality.
And for the paying of the debt belonging to our sinful human condition, His impervious nature was united with our perishable nature; the one true God became true man in the Person of our one Lord, the Son of God born of Mary; so that, as suited the needs of our case, one and the same Mediator between God and men, the Man Christ Jesus, could both die in our stead and raise us with Himself.
Rightly, therefore, did the birth of our Salvation impart no corruption to the Virgin's purity, because the bearing of the Truth was the keeping of honor. Such then, beloved, was the Nativity that was fitting to the Power of God and the Wisdom of God, even Christ, whereby He might be one with us in manhood and surpass us in Godhead. For unless He were true God, He would not bring us a remedy: but unless He were true Man, He would not have been the Savior of men.
Therefore the exulting angels' song when the Lord was born is this, "Glory to God in the Highest," and their message, "peace on earth to men of good will." For they see that the heavenly Jerusalem is being built up out of all the nations of the world. And over that indescribable work of the Divine love, how ought the children of men rejoice, when the joy of the lofty angels is so great?
Let us, therefore, dearly beloved, give thanks to God the Father, through His Son, in the Holy Spirit; Who "for His great mercy, wherewith He has loved us," has had pity on us: and "when we were dead in our sins, He has quickened us together in Christ," that we might be in Him a new creation and live a new life in Christ, in righteousness and purity before Him. Let us put off the old man with his deeds: and having obtained a share in the birth of Christ, let us renounce the works of the flesh.
Dear Christian, acknowledge your dignity in Christ, and, becoming a partner in His Divine nature, refuse to go back to vile baseness of your old, degenerate conduct. Remember the Head and the Body of which you are a member. Recall that you were rescued from the power of darkness and brought into God's light and kingdom. By the Mystery of Holy Baptism, you were made the temple of the Holy Spirit: do not put such a guest to flight by continuing in sin, whereby you would subject yourself once more to the devil's power:
Because your ransom money is the very Blood of Christ; because He shall judge you in truth, Who ransomed you in mercy; Who with the Father and the Holy Spirit reigns for ever and ever. Amen.