In his Romans commentary, Karl Barth develops an image to speak of the relationships between the Law and the Gospel, Jews and gentiles. It relates very well to Paul’s use of Habakkuk and the necessity of faithful gospel improvisation among God’s people. The image also nicely sums up the epochal shift in the death and resurrection of Jesus and the sending of the Spirit.
I like how Barth depicts the freedom of God and the newness of the gospel without denigrating Israel and the Law. The image stresses the necessity of that nimble readiness to hear God’s word afresh and do what God says, no matter how surprising, upsetting, or unpredictable. He works with this image throughout the commentary to develop his Kierkegaardian reading of Romans.
The law is the revelation once given by God, given in its completeness. The law is the impression of divine revelation left behind in time, in history, and in the lives of men; it is a heap of clinkers marking a fiery miracle which has taken place, a burnt-out crater disclosing the place where God has spoken, a solemn reminder of the humiliation through which some men had been compelled to pass, a dry canal which in a past generation and under different conditions had been filled with the living water of faith and of clear perception, a canal formed out of ideas and conceptions and commandments, all of which call to mind the behaviour of certain other men, and demand that their conduct should be maintained. The men who have the law are the men who inhabit this empty canal. They are stamped with the impress of the true and unknown God, because they possess the form of traditional and inherited religion, or even the form of an experience which once had been theirs. Consequently, they have in their midst the sign-post which points them to God, to the KRISIS of human existence, to the new world which is set at the barrier of this world. Thus directed, the stamp of revelation appears to them of such supreme importance that they are busily engaged in preserving its impress. Gentiles which have not the law are they who lack this direction altogether. Their individual lives and their experiences of history are not stamped by revelation; and they have no impress of it to guard. They may be named sleepers, for they are disturbed by no memory of some incomprehensible occurrence in their experience or in the experience of others. They may be named unbelievers, for they do not seem to be moved either to awe or to amazement at that which is above them; they are marked by no visible brokenness. They may be named unrighteous, for they accept the course of the world without question and are unconscious of the barrier which hems them in. In no sense can they be described as inhabiting the empty canal of revelation. But it can happen that the Gentiles, which have not the law, do the things of the law. Because God is the Judge, the doing of the law is a thing distinct from its possession or its hearing (ii. 13). To do the law means that revelation occurs, that God speaks. When a man stands before God, awe and humility are inevitable, and this is the righteousness which is valid with God. But revelation is from God; it cannot be compelled to flow between the banks of an empty canal. It can flow there; but it also fashions for itself a new bed in which to run its course, for it is not bound to the impress which it once made, but is free (pp. 65-66).