“It ought to be the first concern of every Christian to lay aside all confidence in works and increasingly to strengthen faith alone and through faith to grow in the knowledge, not of works, but of Christ Jesus, who suffered and rose for him, as Peter teaches in the last chapter of his first Epistle (1 Pet. 5:10).
No other work makes a Christian. Thus when the Jews asked Christ, as related in John 6:28, what they must do “to be doing the work of God,” He brushed aside the multitude of works which He saw they did in great profusion and suggested one work, saying, “This is the work of God, that you believe in Him whom He has sent” (John 6:29); “for on him has God the Father set his seal” (John 6:27).
Therefore true faith in Christ is a treasure beyond comparison which brings with it complete salvation and saves man from every evil.”
–Martin Luther, The Freedom of the Christian (1520), in Luther’s Works, Vol. 31: Career of the Reformer I (ed. Jaroslav Jan Pelikan, Hilton C. Oswald, and Helmut T. Lehmann; vol. 31; Philadelphia: Fortress Press, 1999), 31: 347.