When we talk about sola scriptura we are talking about the fact that it is God’s Word—and not man’s—that gives us the instruction we need to attain everlasting life. It’s not to say that as Christians we believe you should only read the Bible and nothing else. If your sink gets clogged a plumbing manual will be of more use than anything in the New or Old Testaments. Sola scriptura says that the Bible gives us everything we need to know about everything that matters—i.e., salvation.
Once again, at the time of the Reformation the Roman Catholic Church did not deny the importance of the Word of God, but they certainly denied it’s sufficiency. They said it was not sufficient to reveal to us the way to heaven. Rather, they argued you needed something in addition to Scripture: the traditions of the church. Rome declared in the Council of Trent in the 16th Century: “Scripture and Tradition are actually two forms of God’s Word – ‘written’ and ‘unwritten.’”
What led the Roman Catholics astray was their understanding that the church birthed the Word of God, rather than the Word being the foundation of the church (Eph. 2:20). Yes, God gives us consciences and good sense and even the traditions of the church for which we can glean insight into life, but for salvation it must be Scripture and Scripture alone. How could we even for a moment think we could bring any kind of insight of our own to add to God’s? In his prophecy, Isaiah speaks of God’s Word not retuning “empty” but accomplishing God’s purpose (Is. 55:10). Proverbs 30:6 describes every word of God as true, and, moreover, gives a warning to any who would dare add their own words to it. Similar inscriptural curses in Deuteronomy 4:12, 12:32, and Revelation 22:17-18 show just how seriously God takes the sufficiency of His Word.
In Paul’s second letter to Timothy, he writes: “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work” (2 Tim. 3:16-17). This is Scripture’s greatest defense for its own sufficiency: the fact that the Bible is God’s Word, breathed out by Him, and not man’s.
This concept of the nature of Scripture continued from the time of the Bible’s formation into the age of the ancient church, which is what the Reformation was trying to recover. The great apologist Irenaeus said, “The Scriptures are perfect, inasmuch as they were uttered by the Word of God and His Spirit.” To Augustine is attributed this gem: “Therefore we yield to and agree to the authority of the Holy Scripture which can neither be deceived nor deceive.”
Thus the Reformed creeds and confessions spoke clearly about the necessity of recovering the sufficiency of Scripture. Two are worth quoting at length. First, the Geneva Confession sets forth in Section One:
We affirm that we desire to follow Scripture alone as a rule of faith and religion, without mixing with it any other things which might be devised by the opinion of men apart from the Word of God, and without wishing to accept for our spiritual government any other doctrine than what is conveyed to us by the same Word without addition or diminution, according to the command of our Lord.
The French Confession of Faith from 1559 is equally clear:
We believe that the Word contained in these books has proceeded from God, and receives its authority from Him alone, and not from men. And inasmuch as it is the rule of all truth, containing all that is necessary for the service of God and for our salvation, it is not lawful for me, nor even for angels, to add to it, to take away from it, or to change it.
This was the thrust of the Reformation: turning aside from man and relying fully upon the Word of God. It was a rejection of the notion that the Church had anything to offer toward salvation apart from ministering what the Bible taught. This is why we ensure that our services are filled with Scripture: we sing Scripture, pray Scripture, read Scripture, and preach Scripture because it alone is sufficient for our salvation.