Barth is famous, or infamous, for holding what is sometimes called a 'dynamic' doctrine of revelation. That is to say, rather than locating revelation in one place, and consequently identifying it with the text of Scripture, Barth sees revelation as an event. To be sure, Scripture is the authoritative medium through which revelation occurs, but for Barth revelation is not something that can be pinned down to the pages of the Bible. Revelation is always personal disclosure, one person revealing themselves to another. Consequently, it is always something that happens; an event, not an object.
As an aside, there is a whole ontology at work here; it is not just an oddity of Barth's doctrine of Scripture. Being and doing are closely related in Barth's thinking, correctly in my view.
I do understand why this makes some people uncomfortable. It boils down to the question which I have been asked more than once, with varying degrees of suspicion: is the Bible the word of God or not? The only answer I can give is a very definite yes, qualified at once by a clear no. Is this the place where I must seek God? Is this the place in which he has promised to reveal himself? Yes, it is. But I cannot possess revelation; I can only await it, and - in faith - expect it. There is a serious insecurity here, met only by the security of God's promise.
When it comes to ethics, the problem seems more acute. Here, too, everything is dynamic. Ethics is not a matter of possessing God's commands and working out what to do with them. God's command is always a personal command to me in the here and now. It is not for me to apply; it is for me to obey.
This summer I read Metaxas' excellent biography of Dietrich Bonhoeffer, which really ought to be required reading alongside his theology. Bonhoeffer's own Ethics makes so much more sense when read within the context of his life. For him, ethics was absolutely that: hearing God's word and living in response. Hearing and obeying. Within his own Lutheran context, he was accused of legalism, but it was his ethics which led him into conspiracy to kill Hitler. The word of God, he was convinced, demanded it.
And here is a huge risk. Only a firm belief in justification by faith will prevent me from being paralysed in the face of God's command. What if I have misheard, or misapplied? Well, God is good, and will make good even out of my mistakes. The important thing is to listen and do, and trust his promise to guide.