'The Word of God comes, whenever it comes, in a form that is contrary to our own thinking. ... Unless one becomes acquainted with it through practical experience, he will never understand it. And certainly, if practical experience is necessary in law which teaches a shadowy righteousness, how much more necessary it is in theology.' From Luther: Lectures on Romans (Library of Christian Classics), ed. Wilhelm Pauck (Westminster Press, 1961), 327-8.
Much depth to plumb there!