Christ, the Glorious Mediator
In his Institutes of the Christian Religion [Amazon affiliate link], Calvin writes about Christ, our glorious Mediator. In Book Second, Chapter 12, he writes:
This will become still clearer if we reflect, that the work to be performed by the Mediator was of no common description: being to restore us to the divine favor, so as to make us, instead of sons of men, sons of God; instead of heirs of hell, heirs of a heavenly kingdom. Who could do this unless the Son of God should also become the Son of man, and so receive what is ours as to transfer to us what is his, making that which is his by nature to become ours by grace? Relying on this earnest, we trust that we are the sons of God, because the natural Son of God assumed to himself a body of our body, flesh of our flesh, bones of our bones, that he might be one with us; he declined not to take what was peculiar to us, that he might in his turn extend to us what was peculiarly his own, and thus might be in common with us both Son of God and Son of man. Hence that holy brotherhood which he commends with his own lips, when he says, “I ascend to my Father, and your Father, to my God, and your God” (John 20:17). In this way, we have a sure inheritance in the heavenly kingdom, because the only Son of God, to whom it entirely belonged, has adopted us as his brethren; and if brethren, then partners with him in the inheritance (Rom 8:17). Moreover, it was especially necessary for this cause also that he who was to be our Redeemer should be truly God and man. It was his to swallow up death: who but Life could do so? It was his to conquer sin: who could do so save Righteousness itself? It was his to put to flight the powers of the air and the world: who could do so but the mighty power superior to both? But who possesses life and righteousness, and the dominion and government of heaven, but God alone? Therefore God, in his infinite mercy, having determined to redeem us, because himself our Redeemer in the person of his only begotten Son.
Institutes, Book Second, Chapter 12, Section 2. Hendrickson 2008, pg. 298.