“We have taken it upon ourselves in the Lord’s name to lecture on this Epistle of Paul to the Galatians once more. This is not because we want to teach something new or unknown, for by the grace of God Paul is now very well known to you.
But it is because, as I often warn you, there is a clear and present danger that the devil may take away from us the pure doctrine of faith and may substitute for it the doctrines of works and of human traditions. It is very necessary, therefore, that this doctrine of faith be continually read and heard in public.
No matter how well known it may be or how carefully learned, the devil, our adversary, who prowls around and seeks to devour us (1 Peter 5:8), is not dead. Our flesh also goes on living. Besides, temptations of every sort attack and oppress us on every side.
Therefore this doctrine can never be discussed and taught enough. If it is lost and perishes, the whole knowledge of truth, life, and salvation is lost and perishes at the same time. But if it flourishes, everything good flourishes—religion, true worship, the glory of God, and the right knowledge of all things and of all social conditions.
To keep from doing nothing, we shall begin again where we broke off, according to the saying: ‘When a man has finished, he is just beginning.'”
–Martin Luther, Luther’s Works, Vol. 26: Lectures on Galatians, 1535, Chapters 1-4 (ed. Jaroslav Jan Pelikan, Hilton C. Oswald, and Helmut T. Lehmann; vol. 26; Saint Louis: Concordia Publishing House, 1999), 26: 3.