“Baptism is a very different thing from all other water, not by virtue of the natural substance but because here something nobler is added, for God himself stakes his honor, his power, and his might on it. Therefore it is not simply a natural water, but a divine, heavenly, holy, and blessed water….all by virtue of the Word, which is a heavenly, holy Word that no one can sufficiently extol, for it contains and conveys all that is God’s. This, too, is where it derives its nature so that it is called a sacrament, as St. Augustine taught, ‘Accedat verbum ad sacramentum ad elementum et fit sacramentum,’ which means that ‘when the Word is added to the element or the natural substance, it becomes a sacrament,’ that is, a holy, divine thing and sign.” Martin Luther, The Large Catechism, Fourth Part: Baptism, sections 17-18, in The Book of Concord, eds. Robert Kolb and Timothy J. Wingert (Minneapolis 2000), p. 458.
“It is the Word….that makes this a sacrament and distinguishes it from ordinary bread and wine, so that it is called and truly is Christ’s body and blood. For it is said, ‘Accedat verbum ad elementum et fit sacramentum,’ that is, ‘When the Word is joined to the external element, it becomes a sacrament.’ This saying of St. Augustine is so appropriate and well put that he could hardly have said anything better. The Word must make the element a sacrament; otherwise it remains an ordinary element.” Large Catechism, Fifth Part, The Sacrament of the Altar, sections10-11 in Ibid., p. 468.
In these descriptions of the sacraments Dr Luther follows the medieval definition derived from Augustine’s Tractate 80 on the Gospel of John. Augustine (d. 430) was the bishop of Hippo in Roman North Africa. By Luther’s own admission, Augustine’s theology greatly influenced Luther’s rediscovery of the gospel of grace. In Tractate 80, sec. 3, Augustine examines John 15:3, “Already you are clean because of the word that I have spoken to you.” (ESV)
“Why does He not say, You are clean because of the baptism wherewith you have been washed, but he says, ‘because of the word which I have spoken to you,’ save only that in the water also it is the word that cleanses? Take away the word, and what is the water except water. The word is added [accedit] to the element, and it becomes a sacrament, as if itself a kind of visible word….And whence has water so great a power, as in touching the body to cleanse the heart, unless by the working of the word, not because it is spoken, but because it is believed.” Augustine, Tractates in the Gospel of John 80. 3. Nicene and Post-Nicene Fathers, volume 7, p. 344. I have changed the text slightly in places according to the Latin text in Corpus Christianorum Series Latina, vol. 36, p. 529.
Augustine then quotes Romans 10:10, I Peter 3:21, and Ephesians 5:25-26 to demonstrate the power of God’s Word through preaching and Baptism. Then he concluded: “The cleansing, therefore, would on no account be attributed to the fleeting and perishable element, were it not for that which is added, ‘by the word.’ [Eph. 5:26] This word of faith possesses such power in the Church of God, that through the one who believes, presents, blesses and baptizes, [the word] cleanses even a tiny infant, although itself unable as yet with the heart to believe unto righteousness, and to make confession with the mouth unto salvation. All this is done through the word, whereof the Lord said: ‘Now you are clean through the word that I have spoken to you.’ ” Augustine, NPNF 7:345. Again I have changed the translation based on CCSL 36:529.