At no time is the church in the OT and the NT ever directed to anything other than the always avaiilable Word of God, either written or unwritten. By it alone human beings can have a spiritual life. The church finds all it needs in the Scripture available to it at a given time. Subsequent Scriptures presuppose, link up with, and build upon, preceding Scripture. The prophets and psalmists assume the Torah. Isaiah (8:20) calls everyone to the law and to the testimony. The NT considers itself the fulfillment of the OT and refers back to nothing other than the existing Scripture. Even more telling is the fact that all that lies outside of Scripture is as firmly as possible ruled out. Traditions are rejected as the institutions of human beings (Isa. 29:13; Matt. 15:3,9; 1 Cor. 4:6). The tradition that developed in the days of the OT prompted the Jews to reject the Christ. Over against it Jesus posited his “but I say to you” (Matt. 5:27, 32, 34, 38, 44), and against Pharisees and scribes he again aligned himself with the Law and the Prophets. The apostles appeal only to the OT Scriptures and never refer the churches to anything other than the word of God proclaimed by them. Inasmuch as in the early period tradition sought to be nothing other than the preservation of the things personally taught and instituted by the apostles, it was not yet dangerous. But the Roman Catholic tradition has utterly deteriorated from that level. It cannot be demonstrated that any doctrine or practice is of apostolic origin except insofar as this can be shown from their writings. The Roman Catholic tradition, which gave rise to the mass, to Mariolatry, to papal infallibility, and other Roman distinctives, is nothing but a sanctioning of tha actual state of affairs of the Roman Catholic Church, a justification of the superstition that has crept into it.
Reformed Dogmatics Vol. 1: Prolegomena (Grand Rapids, Michigan; Baker Academic; 2003) p. 489-490.