Q. 39. Why was it requisite that the mediator should be man?
A. It was requisite that the mediator should be man, that he might advance our nature, perform obedience to the law, suffer and make intercession for us in our nature, have a fellow-feeling of our infirmities; that we might receive the adoption of sons, and have comfort and access with boldness unto the throne of grace.
Again these points are commonly understood.
Why was it necessary that the Mediator “partake of flesh and blood,” that is, possess a human nature? Because to redeem the human race, the Mediator must act as the representative of human beings, and in order to be a representative of human beings, he must first of all be a member of the human race. Even in ordinary human organizations, a person cannot be an officer until he was first of all a member of the human race. Since sin and ruin came by man, redemption must come by man too (1 Cor. 15:21: “For since by man came death, by Man came also the resurrection of the dead”).
Why must the Mediator perform obedience to the law? Adapt and Adam and all his posterity had broken the law of God and lived in violation of that law. It was necessary that the second Adam keep the law of God perfectly. God himself is not under the law; he is the lawgiver. Jesus Christ had to be truly human so that he could be truly under the law of God, and thus succeed where Adam failed, in meeting the condition of the covenant of works, namely, a perfect obedience to the law of God.
Rainbow Trout 