Here Christ's declaration applies, "So you also, when you have done all that you were commanded, say, 'We are unworthy servants; we have only done what was our duty' " (Luke 17:10). These words clearly declare that God saves by mercy and because of His promise, not that it is due because of the value of our works... The adversaries are deceived regarding the term faith. If faith would signify historical knowledge that the wicked and the devils also possess, the adversaries would correctly argue that faith is unprofitable when they say: "When we have believed all things, say, 'We are unprofitable servants.' " But we are not speaking of historical knowledge, but of confidence in God's promise and mercy. This confidence in the promise confesses that we are unprofitable servants. Yes, this confession that our works are unworthy is the very voice of faith, as appears in this example of Daniel 9:18, which we cited, "We do not present our pleas before You because of our righteousness." Faith saves because it takes hold of mercy, or the promise of grace, even though our works are unworthy. Understood this way, namely, that our works are unworthy, the word reversal does not injure us: "When you shall have believed all things, say, 'We are unprofitable servants.' " We teach the same as the entire Church when we teach that we are saved by mercy. (paragraphs 213, 216-217)
Condensed from CONCORDIA: THE LUTHERAN CONFESSIONS, copyright 2005,2006 by Concordia Publishing House. Used by permission. All rights reserved. To purchase a copy of CONCORDIA, call 800-325-3040.