J. I. Packer lists three things Christ “as the Mediator, came to do, and that only He, as the God-man, could do.”
- He came to reveal God to men. Before we can know and love God, we must be shown what He is like. In Old Testament times, God’s words, in conjunction with His ordering of events, had indicated something of His nature and character, but no disclosure of this kind could be final and definitive. To bring men to the point where they know that the whole truth about God’s outlook and attitudes has been set before them. a different sort of revelation was needed. Therefore God sent His Son, who perfectly bears His image, and who is perfectly identified with His Father’s purposes of love, to live as a man among men, and so make God perfectly known. …
- He came to redeem men from sin. Scripture knows nothing of the speculation, popular in some places, that the Son of God was made flesh in order to perfect creation. It’s uniform witness is rather that he became man in order to redeem. As He said Himself, ‘the Son of man … came … to give his life as a ransom for many’ (Mark 10:45). Isaiah 53 had foretold that the iniquities of erring men should be put away by the death of a righteous servant of God in their stead. The background here was the Hebrew sacrificial system, instituted by God centuries before to teach the principle that atonement for sin is made by the death of a perfect substitute for the sinner. But where could a perfect, sinless, wholly righteous servant of God be found? None qualified except the incarnate Son of God, who because he was man could be tempted, but because He was God could not and did not sin. …
- He came to restore man to God. God the Son was always ‘in the bosom of the Father’ (John 1:18), enjoying the full riches of His Father’s fellowship, love, and glory…. But the sons of Adam were lost, banished from God’s presence by reason of sin. The Son of God came into the world in order that sinners might come to share His experience of God’s fellowship, love, and glory. He came to seek us where we are in order that He might bring us to be with Him where He is. He came to take us as His own brothers and make us His Father’s adopted sons, that we might see and share the Son’s glory and bear the Son’s own image, the family likeness…. When, as the second God-appointed head of our race, the ‘last Adam’, Christ receives those who by faith receive Him, He introduces them at once into a relationship in which the Father’s view of them corresponds to the Father’s view of Him; for Christ’s sake, and in Christ, the Father, reckons righteousness to them (because Christ is righteous) and accounts them His sons by adoption (because Christ is His son by nature). Following upon this, Christ works in them by His Spirit to transform them into His own likeness and root sin out of them, and some day, this task completed, He will bring them to ‘the holy city, new Jerusalem, where nothing unclean may come, there to enjoy the vision of God and the bliss of knowing Him as their own God and Father for evermore.
From the chapter on The Mediator in 18 Words: The Most Important Words You Will Ever Know.