The adversaries condemn the doctrine taught in the forth, fifth, sixth, and twentieth articles of our Confession, that believers obtain the remission of their sins through Christ, by faith alone, without any merit of their own; and insolently reject these two tenets; first, that we deny that man can obtain remission of his sins through his own merit; and secondly, that we hold, teach, and confess that no one is reconciled to God, or obtains remission of his sins, but through faith in Christ alone.

Now, since this controversy concerns the principal and most important article of the whole Christian doctrine, and as much indeed depends upon this article, which contributes especially to a clear, correct apprehension of all the holy Scriptures, and which alone shows the way to the unspeakable treasure and the true knowledge of Christ; yea, which is the only key to the whole Bible, and without which the poor conscience can have no true, invariable, fixed hope, nor conceive the riches of the grace of Christ;—we therefore pray your Imperial Majesty, graciously to hear us concerning these great, momentous, and all-important subjects, as the nature of the case demands. For, as our adversaries do not understand or know, what is meant in the Scriptures by remission of sin, by faith, grace and righteousness, they have miserably defiled this noble, indispensable, and leading article, without which no one can know Christ; they have entirely suppressed the invaluable treasure of the knowledge of Christ, of his kingdom, and of his grace; and robbed our poor consciences of this noble and great treasure and of this eternal comfort, so valuable and important to them.

But in order to confirm our Confession, and to refute what our adversaries have adducted, we shall, in the first place, show the foundation and reasons upon which both doctrines rest, so that each may be more clearly understood.  (This text is from The Henkel Translation of the Book of Concord, which is the only English translation based on the authoritative German Dresden Edition of 1580, p. 156-157).

From this, we now see what our greatest joy should be and for what, above all, we ought to give thanks to God, namely, that He has enlightened us inwardly through His Word and Spirit and has brought us to a saving knowledge of Christ. The Lord Christ, as “Wisdom” (1 Cor. 1:24), understood best what an inexpressible blessing that was, which is why He rejoiced over it so earnestly and gave thanks to His heavenly Father for it so intensely. We do not understand or ponder it with such seriousness, which is why our spiritual joy and thanksgiving are also so much colder. But this is certain: The more the light of the saving knowledge of God increases, the more the spiritual joy and praise of God also grows within you. Indeed, if the natural light causes us to rejoice when it rises after the dark night, or when we are brought out of the dark dungeon to the very light of day, should not the heavenly, spiritual light of divine knowledge that the Lord God has kindled in our hearts, darkened by nature, cause us to rejoice much more, yes, immeasurably more? The natural light illumines us for a short time in this fleeting life and causes us to participate “with the saints in the light” (Col. 1:12).

As high as heaven is above the earth, so much more precious and noble should we also esteem the heavenly light of divine knowledge than the natural light. The one for whom that heavenly light has not yet appeared and arisen still sits in darkness and will be cast out into the outermost darkness, and the natural light of the sun or of his own understanding will not be able to prevent it; only the heavenly light will do. If we want to come to this light, then we must not place too much trust in the natural light of our understanding, which is deceptive and misleading. We must not consider ourselves wise, but we should recognize that the natural light is darkness before God, and the world’s wisdom is foolishness. Many people fool themselves in this regard; they think that the true, heavenly light of the saving knowledge of God has arisen in their heart, but it is only a slender ray of the natural light which does not go or lead beyond nature. O heavenly Light, shine on us and drive out the darkness from our hearts! O bright Morning Star, arise in our heart! Teach us, O divine Wisdom! We will gladly be infants and willingly yield to Your enlightening!

(Sermon for St Matthias-February 24, Postilla Volume 3 by Johann Gerhard, Repristination Press, page 51-52)