In the third place we want also to consider why it is that our Lord God sends us such suffering. And the reason is that in this way he wants to make us conformed to the image of his dear Son, Christ, so that we may become like him here in suffering and there in that life to come in honor and glory [cf. Rom. 8:29; 8:17; II Tim. 2:11–12], as he says, “Was it not necessary that the Christ should suffer and enter into glory?” [cf. Luke 24:26]. But God cannot accomplish this in us except through suffering and affliction, which he sends to us through the devil or other wicked people. (Luther’s Works, v.51, p.206)

Therefore in affliction every Christian should so arm himself that he may defend and guard himself with the fine, comfortable assurances which Christ, our dear Lord, has left us when we suffer for his Word’s sake. But if we do not do this, if we let the comforting sayings go, then when the cross comes the same thing that happened to Eve in paradise will happen to us. She had God’s commandment and with it she should have beaten down the devil’s suggestions and instigations. But what did she do? She let the Word go and kept thinking what a fine apple it was and that after all such a little thing was of no great importance. So she went her way. And when one lets the Word go, there can be no other result. But when we stay with the Word and hold on to it, we shall certainly have the experience of conquering and coming out of it fine.

You see that we teach these two things [1. that God has appointed that we should suffer and that it cannot be otherwise. 2. We have the promise and assurance that God will keep his Word] when we preach on suffering and cross. And anybody who accuses us of teaching nothing about suffering is doing us an injustice. But this we do not do; we do not make our suffering meritorious before God. No, far from it. Christ alone did that and nobody else, and to him alone belongs the glory. (Luther’s Works, v.51, p.205-206)