If, then, the mass is a testament and sacrament in which the forgiveness of sins and every grace of God are promised and sealed with a sign, it follows self-evidently what is the best preparation for it. Without doubt the mass is given to them that need it and desire it. But who needs forgiveness of sins and God’s grace more than just these poor miserable consciences who are driven and tormented by their sins, are afraid of God’s wrath, judgement, death, and hell, and would be eager to have a gracious God, desiring nothing more greatly than this? These are truly they who are well prepared for the mass. For with them these words have found force and meaning, when Christ says, “Take and drink, this is my blood, which is poured out for you for the forgiveness of sins.” Where such a soul believes these words, as it ought, it receives from the mass all the fruits of the mass, that is, peace and joy, and thus is thereby well and richly fed in spirit.
But where there is no faith, there no prayer helps, nor the hearing of many masses. Things can only become worse. As Psalm 23 says, “Before my eyes thou hast prepared a table for me against all my affliction.” Is this not a clear verse? What greater affliction is there than sin and the evil conscience which is always afraid of God’s anger and never has rest. Again, Psalm 111 says, “He has caused his wonderful works to be remembered, and has provided food for those who fear him.” It is certain, then, that for bold and satisfied spirits, whose sin does not prick them, the mass is of no value. For they have as yet no hunger for this food, since they are still too full. The mass demands and must have a hungry soul, which longs for the forgiveness of sins and divine favour.
But because this despair and unrest of conscience are nothing but an infirmity of faith, the severest malady which man can have in body and soul, and which cannot at once be speedily cured, it is useful and necessary that the more restless a person’s conscience, the more should he go to the sacrament or hear mass. He should do this in such a way as to picture to himself therein the word of God and feed and strengthen his faith by it; never to make a work or sacrifice of it, but let it remain a testament and a sacrament, out of which he shall take and enjoy a benefit freely and of grace. Thereby his heart may become sweet toward God and obtain a comforting confidence toward him. For so sings the Psalter, Psalm 104, “The bread strengthens man’s heart, and the wine gladdens the heart of man.”
Martin Luther, Luther’s Works, Vol. 35: Word and Sacrament I, ed. Jaroslav Jan Pelikan, Hilton C. Oswald, and Helmut T. Lehmann, vol. 35 (Philadelphia: Fortress Press, 1999), 109–110.