[1] Concerning the use of sacraments it is taught that the sacraments are instituted not only to be signs by which people may recognize Christians outwardly, but also as signs and testimonies of God’s will toward us in order thereby to awaken and strengthen our faith. [2] That is why they also require faith and are rightly used when received in faith for the strengthening of faith.

[3] Rejected, therefore, are those who teach that the sacraments justify ex opere operato without faith and who do not teach that this faith should be added so that the forgiveness of sin (which is obtained through faith and not through work) may be offered there

Robert Kolb, Timothy J. Wengert, and Charles P. Arand, The Book of Concord: The Confessions of the Evangelical Lutheran Church (Minneapolis, MN: Fortress Press, 2000), 46.