For this is the difference between the children of God and unbelievers. The latter offer resistance and refuse to endure the discipline of the Lord. But for the godly this discipline is necessary because of the flesh, which is corrupt and is full of sins, smugness, contempt of God, wrath, and lusts. It is because of these that they do not pray, do not believe, do not hope, do not love, and do not trouble themselves about God.
These faults and most serious sicknesses cling to the saints. Therefore to cure them God troubles them, mortifies them, and leads them down to hell. These remedies and works of God are represented everywhere in Holy Scripture and in the examples of the godly. They have never been understood by the world and reason, because the world and reason do not have this book from which to learn this art. Nor is there any other book to teach this than the one in which the Holy Spirit speaks to us in this manner: “I am a God who kills and brings to life, brings down to Sheol and raises up, makes poor and makes rich (cf. 1 Sam. 2:6–7). Not separately or disjunctively. Killing is not the only thing I do. No, this would be devilish. But I am a God who kills and brings to life. I bring down to Sheol, but in such a way that I bring back.”
This should be repeated and urged more often, because it is the special wisdom and teaching of Christians, who should be so stouthearted that no evil can happen to them to prevent them from glorying and triumphing. For they have the Word, absolution, Baptism, the remission of sins, and the promise of eternal life. And whatever adversity must be borne either in death or in hell—no evil is excepted, whether it is an evil inwardly or outwardly—they should say: “I triumph and am proud, because I am lord over death, sin, hell, the world, and all evils, so that for a Christian there is no difference between life and death, wealth and poverty, disgrace and fame. Consequently, he becomes a lord powerful in battle and has been placed above the horror of death, hell, and all adversaries. To be sure, this is not our own doing, because nature cannot accomplish this. But it comes to pass because our Savior, our Lord and Conqueror, the Son of God, sits at the right hand of the Father. He frees, defends, and governs us. Therefore let death terrify us, and let Satan drag us off to hell! What then? My Lord and my Redeemer lives!”
Luther’s works, vol. 8: Lectures on Genesis: Chapters 45-50