“Mystery hidden from the ages” (Col 1:26) And from the nations is now revealed through the true and perfect incarnation of the Son and God. For He united our nature to himself in a single hypostasis, without division, and without confusion, and joined us to himself as a kind of first fruits. This holy flesh with its intellectual and rational soul came from us and is ours. He considered us worthy to be one and the same with himself according to his humanity.
-St. Maximus the Confessor, On the Cosmic Mystery of Jesus Christ
The Incarnation of the Son of God, Jesus Christ, is the mystery, which was in God’s Plan before the ages. It was the central act in this Divine Plan for mankind to become holy and made immortal through communion with the Incarnate Word of God, Jesus Christ. He became man because it was the Divine Plan and mystery before the ages to unite man with God and His life in Christ. Through Satan, the fallen angel, Adam and Eve the first humans were deceived by his thoughts and his evil knowledge that he transmitted to them. They lost the potentiality to attain perfection and immortality because they switched from contemplating the life of God to engaging in self-desires and lust. They brought themselves into a fallen world where they would receive death and would become alienated from God. His creation was wounded by Satan’s deception and was left spiritually and physically ill.
The Word of God came in His own Person, because it was He alone, the Image of the Father, Who could recreate man made after the Image. In order to effect this re-creation, however, He had first to do away with death and corruption. Therefore He assumed a human body, in order that in it death might once and for all be destroyed, and that men might be renewed according to the Image of God. Salvation, or "being saved," therefore, refers to this process of being saved from death and corruption and the fate of eternal death. There is nothing that a person can do to earn salvation. It is rather a gift from God. However, this gift of relationship has to be accepted by the believer, since God will not force salvation on humanity. Man is free to reject the gift of salvation continually offered by God. To be saved, man must work together with God in his entire being, including his will, effort and actions, are perfectly conformed with, and united to, His eternal life.
God becomes powerless before human freedom; He cannot violate it since it flows from His own omnipotence. Certainly man was created by the will of God alone; but he cannot be made holy by Him alone. A single will to raise up the image, but two to make the image into a likeness. The love of God for man is so great that it cannot constrain, for there is no love without respect. The ultimate goal of a Christian is to be in union with God. Salvation therefore is not merely an escape from the eternal bondage of death, but an entrance to participate in Christ’s eternal life.