A Sermon by Pope Saint Leo the Great on the Nativity of Christ. This sermon is read from Volume 12 of Nicene and Post Nicene Fathers, Second Series. This work is in the public domain. The text of sermon read in this podcast is provided below. It has been slightly edited for ease of comprehension.

This Sermon is the Second of eight Sermons on the Nativity written by Pope Saint Leo the Great.

On the Feast of the Nativity II

Part 1. The Mystery of the Incarnation Demands Our Joy

Let us be glad in the Lord, dearly-beloved, and rejoice with spiritual joy that there has dawned for us the day of ever-new redemption, of ancient preparation, of eternal bliss. 

For as the year rolls round, there recurs for us this commemoration of our salvation, which was promised from the beginning. Accomplished in the fulness of time this grace will endure for ever. On this feast we are bound with hearts up-lifted to adore the divine mystery:  so that what is the effect of God’s great gift may be celebrated in the Church’s great rejoicing.  For God the almighty and merciful, immeasurably good and all loving, whose will is power and whose work is mercy, as  soon as the devil’s malevolence killed us by the poison of his hatred, foretold at the very beginning of the world the remedy His devotion had prepared for the restoration of us mortals. It was then he proclaimed to the serpent that the seed of the woman should come to crush his head by its power. This signified no doubt that Christ would come in the flesh, God and man.  Born of a Virgin and through His uncorrupt birth the despoiler of the human stock was foiled. Thus in the whole and perfect nature of true man was true God born, complete in what was His own, complete in what was ours.  And “ours” we call what the Creator formed in us from the beginning and what He undertook to repair.  For the evil that the deceiver brought in and the sin that the deceived allowed had no trace in the Saviour.  Nor did He share in our faults on account of him partaking of man’s weaknesses. He took the form of a slave without stain of sin, increasing the human while not diminishing the Divine.  The “emptying of Himself” whereby the Invisible made Himself visible, and the Creator and Lord of all things took on fragile mortality itself was the condescension of His pity rather than a failing of His Power.

II.  The new character of the birth of Christ explained.

Therefore, when the time came, dearly beloved, which had been fore-ordained for man’s redemption, there entered these lower parts of the world, the Son of God, descending from His heavenly throne and yet not quitting His Father’s glory, begotten in a new order, by a new nativity.  In this new order, being invisible in His own nature He became visible in ours, and He whom nothing could contain, was content to be contained. He who abides before all time began to be in time.  Though the Lord of all things, He obscured His immeasurable majesty and took on Himself the form of a servant.   Being God and beyond all change and suffering, He did not disdain to be man, subjecting Himself to suffering and to death.

By a new nativity He was begotten, conceived by a Virgin, born of a Virgin, yet without carnal desire and without injury to the mother’s chastity.  In this birth that knew no taint of human flesh came the One who was to be the Saviour of men, while at the same time possessing in Himself the nature of human substance.  For since God was born in the flesh, God Himself was the Father, as the archangel witnessed to the Blessed Virgin Mary:  “because the Holy Spirit shall come upon thee, and the power of the most High shall overshadow thee:  and therefore, that which shall be born of thee shall be called holy, the Son of God.” 

The origin is different but the nature alike:  not by intercourse with man but by the power of God was it brought about:  for a Virgin conceived, a Virgin bore a child,