After all, Luther said, even the Devil quotes scripture. Luther drew a sharp distinction between the role of Bible and the role of reason. The Bible convinces us of our total helplessness before God and conveys to us the gospel of salvation in Jesus Christ. Reason, on the other hand, helps us order society in ways that are just and righteous. The Bible and reason are both given to us by God, but we are to use them for different purposes.
Reason plays no part in our salvation.
By the same token, the Bible plays no part in the ordering of our political, economic, or cultural life. To make his point, Luther once declared that it is better to be governed by a wise Turk than by a foolish Christian. Luther rejected the teaching of people like Erasmus, Calvin, and Muentzer that we can use the Bible to build the kingdom of God on earth. So when you hear people say Luther believed that the Bible is all that Christians need for daily life, you can tell them they're wrong. Even if they're Lutherans.