…as it is of the nature of divine revelation that God comes to us veiled, as the Incarnate One (“In our poor flesh and blood, Enclothes Himself the eternal Good”), so is it of the nature of divine action “that God will not deal with us except through external Word and sacrament” (SA III VIII 10). In this recognition of the indissoluble unity of “sign” and “object” [Zeichen und Sache] the danger of spiritualizing is overcome – the danger that lay in what Augustine taught and that since Berengar and Wycliffe captured so many Catholics of the late Middle Ages and since Zwingli and Bucer a large part of the Reformation movement. In this sense what Luther taught on the sacraments is the great overthrow of Augustinianism in the church and the return to the essence [Est] of the New Testament.
from Hermann Sasse, “Word and Sacrament: Preaching and the Lord’s Supper, Letters to Lutheran Pastors No. 42,” July 1956 (trans Norman Nagel in We Confess the Sacraments, Concordia Publishing House 1985, p19).