“All heretics have continually failed in this one point, that they do not rightly understand or know the article of justification. If we had not this article certain and clear, it were impossible we could criticize the pope’s false doctrine of indulgences and other abominable errors, much less be able to overcome greater spiritual errors and vexations. If we only permit Christ to be our Saviour, then we have won, for he is the only girdle which clasps the whole body together, as St. Paul excellently teaches.
If we look to the spiritual birth and substance of a true Christian, we shall soon extinguish all deserts of good works; for they serve us to no use, neither to purchase sanctification, nor to deliver us from sin, death, devil, or hell.
Little children are saved only by faith without any good works; therefore faith alone justifies. If God’s power be able to effect that in one, then he is also able to accomplish it in all; for the power of the child effects it not, but the power of faith; neither is it done through the child’s weakness or disability; for then that weakness would be merit of itself, or equivalent to merit. It is a mischievous thing that we miserable, sinful wretches will upbraid God, and hit him in the teeth with our works, and think thereby to be justified before him; but God will not allow it.”
Martin Luther, “The Table Talk of Martin Luther”