This difference between the Law and the Gospel is the height of knowledge in Christendom. Every person and all persons who assume or glory in the name of Christian should know and be able to state this difference. If this ability is lacking, one cannot tell a Christian from a heathen or a Jew; of such supreme importance is this differentiation. This is why St. Paul so strongly insists on a clean-cut and proper differentiating of these two doctrines.
Martin Luther, “Sermon on Galatians” (New Years, 1532) on Galatians 3:23–24. Source: WA 36.25 transl. in Ewald M. Plass, What Luther Says (Concordia Publishing House: St Louis, 1959), 2.732.
“The article of justification is fragile. Not in itself, of course, but in us. I know how quickly a person can forfeit the joy of the Gospel. In the midst of the conflict when we should be consoling ourselves with the Gospel, the Law rears up and begins to rage all over our conscience. I say the Gospel is frail because we are frail…
What makes matters worse is that one-half of ourselves, our own reason, stand against us. The flesh resists the spirit, or as Paul puts it, “The flesh lusteth against the Spirit.” Therefore… to know Christ and to believe in Him is no achievement of man, but the gift of God. God alone can create and preserve faith in us…. by hearing and thus receiving the message, the truth, the Gospel of Christ. ” – Luther; Galatians Commentary
I passed Luther’s test. Thank God (literally) I am a Christian. (not being sarcastic)