There is a single, unique, and unprecedented event in the world's history: the incarnation of God. God and man were united in the person of Christ and became the divine and extraordinary person of the God-man. Never before has another such person existed, nor will again, in the history of the world and of humanity. In Christ the God-man, two natures have been united: the divine and the human, without confusion, distinct, separate, and independent, each unchanged by the other. Christ, the Son of God, is also the Son of Man--perfect God and perfect Man. He is truly the God-man in the full sense of the word. As God, He is born of God the Father "before all ages." As human, He was born "of the Holy Spirit and the Virgin Mary," the place being Bethlehem in Judea, and the time being one thousand, nine hundred, and ninety-one years ago.
The event of the Incarnation of the Son and Word of God and His retaining both His divine and human natures have made a profound impression, resulting inevitably in much debate. The Third, Fourth, and Sixth Ecumenical Councils dealt with this matter. The Third Ecumenical Council decided with its infallibility to call Christ "Perfect God and perfect man, with a rational soul and body . . . one in divine essence with the Father and of the same essence as humanity."
The hymnologists of our Church express beautifully all that pertains to the God-man Christ. The Theotokion of the stichera of the third tone (Saturday Vespers) speaks about the human birth of Christ, that "He never underwent change or mixture or division, but He guarded the attributes of both natures."
Whereas, the Theotokion of the stichera of the eighth tone (Saturday Vespers) speaks on the same subject more clearly, saying "He that was born of the Father out of time, His Only-begotten Son, He Himself was born of you [i.e., the Theotokos], assuming flesh, God by nature and becoming man in nature for us, not being divided into two persons, but His two natures remaining unconfused."
A few words should be said here about the purpose of the Incarnation of the Son and Word of God. It is very simple. With the disobedience of Adam and Eve, man fell and lost Grace. He was alienated from God. He was expelled from Paradise. In order for fallen human nature to be restored, the Son and Word of God had to assume the whole of human nature completely, to restore it to Heaven through His Resurrection and Ascension. "Carrying deceived human nature upon Your shoulders, O Christ, through Your Ascension You brought it before God and Father." This was the purpose of the Incarnation of the Son of God. As St. Athanasios writes, "God became man in order for us to become godly." No one should think that we humans can become gods and be given a divine nature. No. We can become godly in the moral sense. We return to our first state. The wall of animosity has been torn down between God and Man and communication between them is free.
This section of our Catechism is quite long, important, and difficult to comprehend. We must continue in the next section to see correctly how the Incarnation took place, and what its meaning is. We shall look at quotations from the Gospel and the Holy Fathers concerning the divine and human nature of Christ, in order to understand the relationships between them. It is not possible of course, to deal with this exhaustively, but at least enough can be said that the teaching of the Incarnation of the Son of God does not seem to be arbitrary, but rather based upon Holy Scripture and the truth that the Incarnated God has taught.
Incarnate Christ, we thank You that You accepted to leave Heaven and Your place next to the Father to descend to earth. To be so humiliated. To take human nature upon Yourself and as human, to undergo the Passion and death upon the Cross. We know that You had no other reason to do this than to do it for us. For our salvation. You took upon Yourself all of our sins. With Your Holy Blood, You washed them away upon the Cross. We have not power enough with which to thank You properly. Accept our simple and humble gratitude. Hear our prayer. Make us worthy and enable us to take advantage of Your Incarnation to change our way of life so that we may be raised up with You and come to the Jerusalem Above in the Kingdom of Heaven. Let us always live near You.