“If lusts, greed, and other sins alone were ruling in us, God would not be so angry. But this root and source of all evils [i.e. to doubt and deny His Word and promises] He detests and punishes in an awful manner. In the sacred accounts many kings are praised because of all sorts of good qualities: moderation, generosity, justice, and the like, which human discipline can bring about. What Scripture complains about in regard to them is that they did evil before the Lord, that is, that they disregarded God, who spoke and promised, and worshiped calves and idols, as Jeroboam and others did. For so great is the perversity of the human heart that it accepts strange gods far more readily and eagerly than it maintains that this God, who has revealed Himself through His promises and signs, is truthful. How great a kindness it is that He has redeemed us through His Son!

“But how difficult it is for us to believe this can be seen in the perils of the plague, famine, exile, and punishments in which we, utterly without any confidence, are troubled and alarmed to the point of being virtually without any hope and promise! What is the reason? Because on account of original sin there is inherent in us this evil which causes our heart to cry out continually against the promises of God and to grumble that familiar charge: ‘God is lying; His oath is not true.’

“If we were able to believe firmly that God will keep His promises and that the oath with which He has pledged His Deity and has given His Son as a sign will be sure, then we would regard death, want, shame, and hell as if they were life, riches, glory, and heaven, just as they differ in no wise before God. But because this does not happen, it is a sure proof of our unbelief and mistrust.

“Therefore the [various pagans and false saints] believe absolutely nothing at all. Nor do they understand what sin, mercy, righteousness, truth, and grace are; all these are mere puzzles for them. Yet they want to appear wise, and they are indeed, but in their way, namely, in philosophy, not in the Kingdom of Heaven, because they have absolutely no understanding of spiritual matters but despise them.

“And how would they care about them and be greatly affected by them when we, who want to be godly, find that awful evil in us that we do not rejoice every moment in spirit over that inexpressible mercy of God toward us and do not laugh at and despise death, the world, and the devil?

“But this serves to glorify the marvelous patience and mercy of God, who forgives not only past but also present sins and with great tenderness of heart puts up with this common indifference toward His grace.

“We have Christ’s command. To it a promise is attached. At the same time there is a threat. ‘Everyone who acknowledges Me before men,’ He says, ‘I also will acknowledge before My Father who is in heaven’ (Matt. 10:32). ‘He who does not take his cross and follow Me is not worthy of Me’ (Matt. 10:38). In John 12:25-26 He says: ‘He who hates his life in this world will keep it for eternal life. If anyone serves Me, he must follow Me; and where I am, there shall My servant be also.’

“Those who are not moved by these and similar statements but put the welfare of the body and the goods of this life ahead of acknowledging Christ assuredly do not hold any other opinion than that God is untruthful when He promises or threatens.

“How often is it repeated in the Psalms: ‘Wait for the Lord; be strong, and let your heart take courage; wait for the Lord!’ (Ps. 27:14). ‘Love the Lord, all you His saints! The Lord preserves the faithful but abundantly requites him who acts haughtily. Be strong, and let your heart take courage, all you who wait for the Lord!’ (Ps. 31:23-24). We know all this, and it is pointed out to us daily; yet we neither believe nor follow God, who calls us to confess the Word and promises help and deliverance. There certainly is no reason for us to think that God is pleased with that doubt and mistrust in us. Indeed, this one sin is by far the gravest of all the sins which will condemn the world and the unbelievers. For the magnitude of the sin can be gauged from the magnitude of God’s promise, oath, pledge, and imprecation.

“Therefore whoever has either a droplet or a spark of that spiritual trust should know that it is a blessing of God and an extraordinary gift. If we firmly and unquestioningly held promises of this kind as true, there would be given to our hearts strength far greater than our fear of the world or the devil or all the gates of hell.

“Accordingly, these things are dealt with rather frequently [in the Holy Scriptures], in order that we may stir up our hearts and finally begin to learn at least with the abecedarians; for we shall never be doctors and rabbis in this wisdom. Would that we were pupils of Christ!”

(Luther’s Lectures on Genesis 22:16, Luther’s Works AE Vol. 4, pp. 146-147)