Examples like this are recounted to us for the purpose of teaching and consolation, and for the strengthening of our faith, in order that we may consider the immeasurable mercy of God, who has saved not only the righteous—namely, Abraham, Isaac, and Jacob—but also the unrighteous—namely, Judah, Tamar, Reuben, Simeon, and Levi, who were outstanding sinners. Consequently, no one should be presumptuous about his own righteousness or wisdom, and no one should despair on account of his sins.Therefore in the Holy Scriptures the most beautiful examples of the fathers—Abraham, Isaac, and Jacob—are celebrated. These men were lights, so to speak, of the whole world and of the church of God. They were like stars, the sun, the dawn; they were perfect in faith, hope, and love. But at the same time outstanding and horrible sinners are described. They were as evil and foul as the former were righteous. Reuben’s wickedness toward his father is just as great in its way as Abraham’s righteousness is great in its way. In this way the righteousness of the foremost saints and the sin of the most evil men are set before us, who have come from one strain and from the same blood. This is the preaching of repentance and faith or of the forgiveness of sins, lest anyone be presumptuous because of his own righteousness and lest those who have fallen despair. For the errors of Judah and also of the other fathers, yes, their enormous failings, are related. And in this manner souls disturbed because of the consciousness of sin must be buoyed up: “Do not despair, for God orders you to have confidence and to believe His promise; and He can also justify, sanctify, and save you, just as He has saved others. He is the same God who humbles the proud and exalts the humble (cf. Luke 1:52). But He does not want us to rely on our own righteousness or to despair in our sins; He wants us to trust in His mercy.” Accordingly, the church of God has great need of these examples. For what would become of us? What hope would be left for us if Peter had not denied Christ and all the apostles had not taken offense at Him, and if Moses, Aaron, and David had not fallen? Therefore God wanted to console sinners with these examples and to say: “If you have fallen, return; for the door of mercy is open to you. You, who are conscious of no sin, do not be presumptuous; but both of you should trust in My grace and mercy.

Martin Luther, vol. 7, Luther’s Works, Vol. 7 : Lectures on Genesis: Chapters 38-44, ed. Jaroslav Jan Pelikan, Hilton C. Oswald and Helmut T. Lehmann, Luther’s Works, Ge 38:5 (Saint Louis: Concordia Publishing House, 1999).