Here courtesy of Stand to Reason Blog is Martin Luther discussing divine mercy:
It is an evangelical word and the sweetest comfort in every way for miserable sinners, where Ezekiel [Ezek. 18:23, 32] says: “I desire not the death of a sinner, but rather that he may turn and live,” like Psalm 28[30:5]: “For his anger is but for a moment, and his favor is for a lifetime.” Then there is Psalm 68[109:21]: “How sweet is thy mercy, O Lord.” and “For I am merciful” [Jer. 3:12], and also Christ’s saying in Matthew 11[:28]: “Come unto me, all you who labor, and I will give you rest,” and that in Exodus 20[:6]: “I show mercy to many thousands, to those who love me.” What, indeed, does almost more than half of Holy Scripture contain but sheer promises of grace, in which mercy, life, peace, and salvation are offered by God to men? And what else do words of promise have to say but this: “I desire not the death of a sinner”? Is it not the same thing to say, “I am merciful,” as to say, “I am not angry, I do not want to punish, I do not want you to die, I want to pardon, I want to spare”? And if these divine promises were not there to raise up consciences afflicted with the sense of sin and terrified with the fear of death and judgment, what place would there be for pardon or hope? What sinner would not despair?…
He does not say, “I desire not the sin of a man,” but, “I desire not the death of a sinner,” plainly showing that he is speaking of the penalty of sin, which the sinner experiences for his sin, namely, the fear of death. And he lifts up and comforts the sinner from his affliction and despair, so as not to quench the smoking flax and break the bruised reed [Isa. 42:3], but to give hope of pardon and salvation, so that he may rather be converted (by turning to salvation from the penalty of death) and live, that is, be at peace and happy with an untroubled conscience.