Before the incarnation of the Son of God, men were not yet prepared spiritually and mentally to acknowledge the divine grace as God's Self-Giving in its deep meaning. It was enough that God had revealed His friendship to man, and attributed Himself to His people especially to those who were close to Him, who accepted Him as the "Source of life."
In the New Testament the grace of God is revealed more clearly together with the Trinitarian faith, for these two facts are correlated to each other.
The Father who is love (1 John 4:8 ), practices His infinite love eternally as He begot His Word, His wisdom, or His Only- Begotten Son, not outside His essence, but as One with Him in the same essence (John 17:21-26). Through this practical eternal love God the Father created man through His Love (John 1:3), and when man fell and his nature was spoiled, God sent His Word to him to give His life up for him and to restore his nature. The Word of God was incarnated and dwelt among men (John 1:14) as their heavenly Friend to redeem them. He united them to Himself as members of His Body, and thus they were prepared to receive the adoption to the Father in Him. The Holy Spirit, who is the Spirit of the Father and the Son at the same time dwelt in man, uniting him with the Father in Jesus Christ, preparing him as a bride to the heavenly wedding-feast, and as a son to enjoy his Father's glories.
Thus the redeeming grace of the Holy Trinity is in fact one integral and inseparable action, I mean God's Self-Giving to man. The Father loved us as His own children, granted us Himself as the true Father; the Son granted us His crucified and risen life to enjoy the adoption; and the Holy Spirit granted us His descent into our souls to practice our adoption to God. The message of the Holy Trinity's redeeming action is our attainment of God within our hearts, uniting Himself with us, declaring that He is ours and we are His own.
Fr. Tadros Yacoub Malaty, 1992