75 Suppose you say, “What shall I do if I cannot feel this need or experience hunger and thirst for the sacrament?” Answer: For persons in such a state of mind that they cannot feel it, I know no better advice than to suggest that they put their hands to their bosom and ask whether they are made of flesh and blood. If you find that you are, then for your own good turn to St. Paul’s Epistle to the Galatians and hear what are the fruits of the flesh: “The works of the flesh are plain: adultery, immorality, impurity, licentiousness, idolatry, sorcery, enmity, strife, jealousy, anger, selfishness, dissension, party spirit, envy, murder, drunkenness, carousing, and the like.”
76 If you cannot feel the need, therefore, at least believe the Scriptures. They will not lie to you, and they know your flesh better than you yourself do. Yes, and St. Paul concludes in Rom. 7:18, “For I know that nothing good dwells within me, that is, in my flesh.” If St. Paul can speak thus of his flesh, let us not pretend to be better or more holy.
77 But the fact that we are insensitive to our sin is all the worse, for it is a sign that ours is a leprous flesh which feels nothing though the disease rages and rankles.
78 As we have said, even if you are so utterly dead in sin, at least believe the Scriptures, which pronounce this judgment upon you. In short, the less you feel your sins and infirmities, the more reason you have to go to the sacrament and seek a remedy.
79 Again, look about you and see whether you are also in the world. If you do not know, ask your neighbors about it. If you are in the world, do not think that there will be any lack of sins and needs. Just begin to act as if you want to become good and cling to the Gospel, and see whether you will not acquire enemies who harm, wrong, and injure you and give you occasion for sin and wrong-doing. If you have not experienced this, then take it from the Scriptures, which everywhere give this testimony about the world.
80 Besides the flesh and the world, you will surely have the devil about you. You will not entirely trample him under foot because our Lord Christ himself could not entirely avoid him.
– Large Catechism, Sacrament of the Altar, V.75-80