Grace and Peace: Sum of Christianity

These two words, grace and peace, contain the sum total of Christianity: grace, the forgiveness of sins; peace, a quiet and joyous conscience. But peace of conscience can never be had unless sin is first forgiven. However, sin is never forgiven because of the fulfilling of the Law, for no man is able to satisfy the Law. The Law rather shows sin and accuses and terrifies the conscience, declares the wrath of God, and drives to desperation....

In short, the works do not exist that can take away sin; but sin is rather increased by works. For the more those who try to justify themselves by works labor and sweat to remove sin, the worse their burden of sin becomes. For only grace can remove sin, and there simply is no other way to remove it.

Source: Quoted in Ewald M. Plass, What Luther Says, A Practical In-home Theology for the Active Christian. St. Louis: Concordia Publishing House. 1959 Edition, 10th Printing (1994), pp. 605-605.