Therefore he says in opposition to both: “I am neither afraid of you, nor will I rejoice with you, for there are other things that I fear and other things in which I will rejoice; I fear Him who can destroy into hell, and not the princes who kill the body (Matt. 10:28). And I will rejoice at the words of God, and not at the presence of your pleasure.” He compares himself to one finding many spoils. And how does he rejoice, I ask? I think that he rejoices in the manner which the Lord describes in Matt. 13:44, that a man who found a treasure hidden in a field hid it and went for joy, etc. He rejoices, but not openly. He alone knows his joy, because he alone knows his good. If he had published it, then the field would certainly not have been sold to him, and he would not have gained possession of the treasure. Or if he had possessed it, he would have possessed it with danger. Such is the joy of the Spirit, because it is in secret, because he alone knows, because also he alone knows his spiritual good. (Luther’s Works, v. 11, p.519)

162. I will rejoice at Thy words like one who has found great spoil. Our every rejoicing is in the hope of things to come, and not in the reality of things present. For this reason we rejoice, because we believe the divine promises, and we hope for and love the things which He promises. For he does not say “I will rejoice at the riches of the world” but “at Thy words.” And it is the voice of the church living among persecutors. For all persecutors did this to lure the faithful to the vanities of the world and passing joys, so that they would either rejoice with them in the worst things, or at least fear them, if they were unwilling to rejoice. And so they attempted to force to joys through grief, to delights through afflictions, to pleasures through torments. (Luther’s Works, v. 11, p.518-519)