"where in the Old Testament we find Israel, or the king of Israel, in the New Testament we find the one Israelite Jesus. He is the object of the same electing will of the Creator, the same merciful divine faithfulness. He is bound to the same obedience and service of God. He is the Son of the Father with the same singularity and exclusiveness. Of course, what is and takes place between Him and the Father is relatively much greater, and as the self-humiliation of God much more singular, than anything indicated by the father-son relationships of the Old Testament. For this one man—it is as if the framework is now filled out and burst through—is the Son of God who is one with God the Father and is Himself God. God is now not only the electing Creator, but the elect creature. He is not only the giver, but also the recipient of grace. He is not only the One who commands, but the One who is called and pledged to obedience. He does not merely go into lowliness, into the far country, to be Himself there, as He did in His turning to Israel. But now He Himself becomes lowly. He Himself is the man who is His Son. He Himself has become a stranger in Him. And Israel and its kings and priests were only the provisional representatives of this incomparable Son. The mystery of Israel was merely the proclamation, which had still to be unriddled, of the real mystery which unriddles itself from within. In the Old Testament we cannot find anything more than these representatives. But we must not overlook these representatives. The Old Testament, and also the New Testament in its constant implicit and explicit connexion with the Old, makes it quite clear that for all its originality and uniqueness what took place in Christ is not an accident, not a historical novum, not the arbitrary action of a Deus ex machina, but that it was and is the fulfilment—the superabundant fulfilment—of the will revealed in the Old Testament of the God who even there was the One who manifested Himself in this one man Jesus of Nazareth—the gracious God who as such is able and willing and ready to condescend to the lowly and to undertake their case at His own cost."
Karl Barth, CD IV/1, trans. Bromiley, 170 =KD IV/1, 185-186 (§59).