Paraphrased/quoted from Karl Barth, Church Dogmatics, 4.1, pp. 185ff.
In the incarnation, the eternal Son of God makes His way into a far country, and takes on the form of a servant. “But the incarnation, the taking of the form of the servant, means not only that God becomes a creature, a man. It means also that He gives Himself up to man’s rebellion against God, placing Himself under the judgment under which man has fallen in his rebellion, under the curse of death which rests upon Him.”
“But at this point what is meant to be supreme praise of God can in fact become supreme blasphemy. God gives Himself, but He does not give Himself away. He does not give up being God in becoming a creature, in becoming man. He does not cease to be God. He does not come into conflict with Himself. He does not sin when in unity with the man Jesus, He mingles with sinners and takes their place. And when He dies in His unity with this man, death does not gain any power over Him. He exists as God in the righteousness and the life, in the obedience and resurrection of this man. He takes as His own the being of man who is in rebellion against God, but He does not make common cause with human rebellion. He takes as his own the being of man under the curse, but in order to do away with it. He acts as Lord over this rebellion even as He subjects Himself to it. He frees the creature in becoming a creature. He overcomes the flesh in becoming flesh. God reconciles the world to Himself because He is in Christ.”
“He is not untrue to Himself but true to Himself in this condescension, as He goes into the far country. If it were otherwise, if in the incarnation God set Himself in contradiction with Himself, how then could he reconcile the world with Himself? Of what value would His deity be to us if – instead of crossing in that deity the very real gulf between Himself and us – He left the deity behind Him, if it came to be outside of Him as He became ours? What would be the value of His journey into the far country if in the course of the journey He lost Himself? If He gave up Himself in coming to us, if He contradicted Himself in going into the far country, then He could only confirm and strengthen man’s rebellion against Him. A God who found Himself in this contradiction could only be the image of our own unreconciled humanity that is projected out onto God.”
But how can the incarnation not be a contradiction in God? Jesus says He does not do His will, but the will of the Father who sent Him. But how can the commanding Lord become an obedient servant without betraying His Lordship? Some have concluded that this obedience and servitude is merely the attitude of the man Jesus of Nazareth. For some, Jesus’ obedience is not the obedience of God – for how can God be obedient? Jesus’ obedience is the obedience of the human nature of Jesus, and the human nature alone. But this cannot be. This would mean that the work of Jesus is not God’s own work. And if the work of Jesus is not God’s own work, then we are still in our sins. But, “if God is in Christ, if what the man Jesus does is God’s own work, that means the self-emptying and self-humbling of Jesus Christ, the obedience of Jesus Christ, is not alien to God Himself.” Paradoxical as it may sound, we must embrace this truth of Christmas, this fundamental truth of the gospel: That it reveals to us the reality of Lordly obedience. “The Eternal Son becomes servant, but in becoming servant He does not cease to be Lord.”
“If we speak of an obedience which takes place in God, then don’t we have to speak necessarily of two divine beings, and of two divine beings who are not equally divine? Do we not have to say that the obedient one is divine only in an improper sense?” Historically, the church, following Scripture, has said otherwise. The obedient Son is as divine as the commanding Father; the obedient Son is the eternal, almighty, omniscient, holy God. In affirming with Scripture that the Son is eternal God, the church has said that obedience is a possibility and actuality in God Himself. The obedience of Jesus points to the obedience of the eternal Son, and is the obedience of the Son, the Son who is equal to the Father, who is One with the Father, who yet obeys the Father. And the Son does not obey only after He has become incarnate. The incarnation is itself an act of obedience, the Son accepting the commission from the Father.
“God is God in these three Persons which cannot be separated, which cannot be autonomous, which cannot cease to be different. He is God in their concrete relationships the one to the other, in the history that takes place between them. The true and living God is the One whose Godhead consists in this history, who is in these three Persons the One God, the Eternal, the Almighty, the Holy, the Merciful, the One who loves in His freedom and is free in His love.”
“His speaking and activity and work in the world consist in the fact that He gives to the world created by Him, to man, a part in the history by which He is God. Scripture teaches that there is in God’s act of creation a reflection of God; that in the difference between Creator and creature there is an image and likeness of the inner life of God Himself. In the work of reconciling the world with God the inward divine relationship between the Father who rules and commands in majesty and the Son who obeys in humility is identical with the very different relationship between God and one of His creatures, a man.”
“God goes into the far country so that man can be brought into the history of the three persons.. He becomes what He had not previously been. He takes into unity with His divine being a quite different, a creaturely and indeed sinful being. To do this He empties Himself, He humbles Himself. But, as in His action as Creator, so in the incarnation: He does not become man apart from a basis in His own being, in His own inner life. What He does by going into the far country corresponds to the history in which He is eternally God. He does not need to deny, let alone abandon and leave behind and diminish His divinity to do this. He does not need to leave the work of reconciliation in the doubtful hands of a creature. He can enter Himself, seeing He is in Himself not only the One who rules and commands in majesty but also in His own divine being, the One who obeys in humility.”
In short, in going to the far country and being obedient to the Father as the Incarnate Son, the Son “does not change. He simply activates and reveals Himself in the world for what He truly is. He is in and for the world what He is in and for Himself. He is in time what He is in eternity, and He is what He is in time because of what He is in eternity. He is in our lowliness what He is in His majesty, and He can be what He is in our lowliness because His majesty is also lowliness. He is as man, as the man who is obedient in humility, exactly what He is as God. This is the true deity of Jesus Christ, His obedience in humility, in His unity and equality with the One who sent Him and to whom He is eternally obedient.”