The design of God in the Incarnation
I. 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 the commemoration of our salvation, which promised from the beginning, accomplished in the fullness of time will endure for ever; on which 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 by the Church's great rejoicings. For God the almighty and merciful, Whose nature as goodness, Whose will is power, Whose work is mercy: as soon as the devil's malignity killed us by the poison of his hatred, foretold at the very beginning of the world the remedy His piety had prepared for the restoration of us mortals: proclaiming to the serpent that the seed of the woman should come to crush the lifting of his baneful head by its power, signifying no doubt that Christ would come in the flesh, God and man, Who born of a Virgin should by His uncorrupt birth condemn the despoiler of the human stock. 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 what the deceiver brought in and the deceived admitted had no trace in the Saviour. Nor because He partook of man's weaknesses, did He therefore share our faults. He took the form of a slave without stain of sin, increasing the human and not diminishing the Divine: because that emptying of Himself whereby the Invisible made Himself visible and Creator and Lord of all things as He was, wished to be mortal, was the condescension of Pity not the failing of Power.
II. The new character of the birth of Christ explained
Therefore, when the time came, dearly beloved, which had been fore-ordained for men's redemption , there enters 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 a new order, because being invisible in His own nature He became visible in ours, and He whom nothing could contain, was content to be contained: abiding before all time He began to be in time: the Lord of all things, He obscured His immeasurable majesty and took on Him the form of a servant: being God, that cannot suffer, He did not disdain to be man that can, and immortal as He is, to subject Himself to the laws of death. And by a new nativity He was begotten, conceived by a Virgin, born of a Virgin, without paternal desire, without injury to the mother's chastity: because such a birth as knew no taint of human flesh, became One who was to be the Saviour of men, while it possessed in itself the nature of human substance. For when 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 you, and the power of the most High shall overshadow you: and therefore, that which shall be born of you shall be called holy, the Son of God Luke 1:35 . The origin is different but the nature like: not by intercourse with man but by the power of God was it brought about: for a Virgin conceived, a Virgin bare, and a Virgin she remained. Consider here not the condition of her that bare but the will of Him that was born; for He was born Man as He willed and was able. If you inquire into the truth of His nature, you must acknowledge the matter to be human: if you search for the mode of His birth, you must confess the power to be of God. For the Lord Jesus Christ came to do away with not to endure our pollutions: not to succumb to our faults but to heal them. He came that He might cure every weakness of our corruptness and all the sores of our defiled souls: for which reason it behooved Him to be born by a new order, who brought to men's bodies the new gift of unsullied purity. For the uncorrupt nature of Him that was born had to guard the primal virginity of the Mother, and the infused power of the Divine Spirit had to preserve in spotlessness and holiness that sanctuary which He had chosen for Himself: that Spirit (I say) who had determined to raise the fallen, to restore the broken, and by overcoming the allurements of the flesh to bestow on us in abundant measure the power of chastity: in order that the virginity which in others cannot be retained in child-bearing, might be attained by them at their second birth.
Nicene and Post-Nicene Fathers, Second Series, ed. by Philip Schaff and Henry Wace (Buffalo, NY: Christian Literature Publishing Co., 1895), transl. by Charles Lett Feltoe, vol. 12, pp. 129-130