On the same day Luther spoke admirably about the future eternal life and its unspeakable joy: “Human reason can’t grasp it by speculation. With our thoughts we can’t get beyond the visible and physical. No man’s heart comprehends eternity. One might suppose that according to the saying, ‘Even pleasure becomes burdensome,’ one would get tired of eternity. What pleasure is like in eternity we can’t imagine. Isaiah said, ‘Be glad and rejoice forever in that which I create’ [Isa. 65:18].” (Luther’s Works, v. 54, p.325)

When the illness of his daughter became graver he [Martin Luther] said, “I love her very much. But if it is thy will to take her, dear God, I shall be glad to know that she is with thee.”

Afterward he said to his daughter, who was lying in bed, “Dear Magdalene, my little daughter, you would be glad to stay here with me, your father. Are you also glad to go to your Father in heaven?”

The sick girl replied, “Yes, dear Father, as God wills.”

The father said, “You dear little girl!” [Then he turned away from her and said,] “The spirit is willing, but the flesh is weak [Matt. 26:41]. I love her very much. If this flesh is so strong, what must the spirit be?” Among other things he then said, “In the last thousand years God has given to no bishop such great gifts as he has given to me (for one should boast of God’s gifts), I’m angry with myself that I’m unable to rejoice from my heart and be thankful to God, though I do at times sing a little song and thank God. Whether we live or die, we are the Lord’s [Rom. 14:8]—in the genitive singular and not in the nominative plural.” (Luther’s Works, v. 54, p.430)

“The world must be considered carefully [Martin Luther said]. It’s governed by opinions, and therefore it’s ruled by sophistical hypocrisy and tyranny. True religion is compelled to serve them as a maidservant. One must therefore be careful and beware of sophistry, which consists not only of equivocation in words but flourishes under all circumstances, so that in religion it possesses a magnificent pretense under the guise of Holy Scripture. There’s more harm in sophistry than any man can perceive; our nature, which is prone to lying, can’t see the evil in sophistry at all. Plato offers a remarkable description of sophistry: People who can twist everything, repudiate the opinions of others, and draw conclusions on both sides after the manner of Carneades are not to be praised. These are sly tricks. It’s the glory of a good character [on the other hand] to seek the truth and to rejoice in guilelessness.” (Luther’s Works, v. 54, p.322)

“A Christian should and must be a cheerful person. If he isn’t, the devil is tempting him. I have sometimes been grievously tempted while bathing in my garden, and then I have sung the hymn, ‘Let us now praise Christ.’ Otherwise I would have been lost then and there. Accordingly, when you notice that you have some such thoughts, say, ‘This isn’t Christ.’ To be sure, he can hear the name of Christ, but it’s a lie because Christ says, ‘Let not your hearts be troubled [John 14:27]. Trust in me,’ etc. This is a command of God: ‘Rejoice!’  I now preach this, and I also write it, but I haven’t as yet learned it. But it happens that we learn as we’re tempted. If we were always glad, the devil would befoul us.  Christ knows that our hearts are troubled, and it is for this reason that he says and commands, ‘Let not your hearts be troubled.’ (Luther’s Works, v. 54, p.95)

I asked him [Martin Luther] about a certain man who, when he had a stomachache for several days and as a consequence had pain in his head and was confused in his thoughts, got the notion and was afraid that he was falling into a state of melancholy. He disclosed his anxiety to me and asked that I notify the doctor, whereupon he [Martin Luther] responded with these words: “When the devil can bring this about, it means that imagination has produced the effect. On this account his thoughts ought to be changed. He ought to think about Christ. You should say to him, ‘Christ lives. You have been baptized. God is not a God of sadness, death, etc., but the devil is. Christ is a God of joy, and so the Scriptures often say that we should rejoice, be glad, etc. This is Christ. Because you have a gracious God, he won’t take you by the throat.’

“A Christian should and must be a cheerful person. If he isn’t, the devil is tempting him. (Luther’s Works, v. 54, p.95)