I have often stated above and elsewhere that it pleases me greatly and is salutary for us to hear of the weaknesses of the saints, for these examples of weakness are more necessary for us and bring more consolation than the examples of that heroic and very great fortitude and other virtues. Thus the fact that David killed Goliath, a bear, a lion, etc., does not edify me much. For I cannot imitate such things, since they surpass my strength and all my thinking. Although they commend the saints in their strength and heroic fortitude, they do not concern us; for they are too sublime for us to be able to match or imitate them. But when examples of weakness, sins, trepidation, and trials are set forth in the saints—as when I read David’s complaints, sobs, fears, and feelings of despair—they buoy me up in a wonderful manner and give great consolation. For I see how they, fearful and terrified though they were, did not perish but buoyed themselves up with the promises they had received; and from this I conclude that there is no need for me to despair either. For in this struggle with hell, in fears and struggles of conscience, they feel and speak as if they had no promises at all. Nevertheless, they are finally preserved and sustained by the Word.
Martin Luther, Lectures on Genesis, Luther’s Works Volume 5, page 254