According to its substance, therefore, the mass is nothing but the aforesaid words of Christ: “Take and eat, etc.”, as if he were saying: “Behold, O sinful and condemned man, out of the pure and unmerited love with which I love you, and by the will of the Father of mercies, apart from any merit or desire of yours, I promise you in these words the forgiveness of all your sins and life everlasting. And that you may be absolutely certain of this irrevocable promise of mine, I shall give my body and pour out my blood, confirming this promise by my very death, and leaving you my body and blood as a sign and memorial of this same promise. As often as you partake of them, remember me, proclaim and praise my love and bounty toward you, and give thanks.”
From this you will see that nothing else is needed for a worthy holding of mass than a faith that relies confidently on this promise, believes Christ to be true in these words of his, and does not doubt that these infinite blessings have been bestowed upon it. Hard on this faith there follows, of itself, a most sweet stirring of the heart, whereby the spirit of man is enlarged and enriched (that is love, given by the Holy Spirit through faith in Christ), so that he is drawn to Christ, that gracious and bounteous testator, and made a thoroughly new and different man. Who would not shed tears of gladness, indeed, almost faint for joy in Christ, if he believed with unshaken faith that this inestimable promise of Christ belonged to him? How could he help loving so great a benefactor, who of his own accord offers, promises, and grants such great riches and this eternal inheritance to one who is unworthy and deserving of something far different?
Martin Luther, Luther’s Works, Vol. 36: Word and Sacrament II, ed. Jaroslav Pelikan, Hilton C. Oswald, and Helmut T. Lehmann, vol. 36 (Philadelphia: Fortress Press, 1999), 40–41.