You know the passage that says taking a census is wrong. Remember? Right. Nothing in the Bible says taking a census is wrong. Yet David was wrong for taking a census in 1 Chronicles 21. God killed 70,000 in Israel with pestilence because of David's census taking. Other census were taken without such a punishment. Other passages even allow for a census, and yet David's census was wrong. How was he supposed to know? We know it was a sin (vv. 1, 8, 17). But what passage did he violate? None. Again, how was he supposed to know?
David was supposed to apply Scripture. His census wasn't living by faith. Chapters 18-20 recount the military victories that God gave David, showing God's protection in fulfillment of the Davidic covenant (1 Chronicles 17). God defeated the foreign nations as a part of His promise. And then David numbers the people (chapter 21). We don't know the particulars of how David wasn't living by faith---it was either that he was taking undeserved credit, fearful for the future, or both. It is assumed that David was to have known this was wrong. We are responsible for applying Scripture. We are to know that certain actions are not acting in faith or are acting in faith, even though the Bible doesn't say one way or another.
Was punishing David for something that the Bible doesn't and didn't forbid "exceeding that which is written"? Was it adding to Scripture, thereby subtracting from the effectiveness of the Bible in David's life? Obviously not. The passage provides a paradigm for applying truth. God has revealed truth. He expects us to understand it and apply it. Would God have killed 70,000 Israelites if it wasn't something that He knew David could apply? Again, of course not.
One passage used by evangelicals to justify their lack of application is 1 Corinthians 4:6, where they will quote from the New American Standard Version, "learn not to exceed what is written," which the King James translates, "not to think of men above that which is written." The text there gives one particular point about our evaluation of men, making sure not to judge leaders outside of a scriptural evaluation. There we go. But that has become a proof text for only judging where the Bible has something specifically to say about it. What occurs, of course, is that passage is ironically applied only in areas that fit favorably with an evangelical's church growth methods.
You can't judge music, because there is no play button in the Bible to tell us what is right music, so if you judge music you are "exceeding what is written." If you judge art, you are exceeding what is written. If you judge dress, you are exceeding what is written. And so on. But what was written about NOT numbering the people? Nothing. And yet God killed 70,000 people. Obviously God wanted David to judge in an area about which nothing was written. He was required to apply Scripture, to apply "living by faith" and "trusting God" to not numbering the people.
God won't usually kill 70,000 for not applying Scripture, but He does expect us to apply it. We are responsible to do so, and we are not exceeding Scripture to do so. We will give an account for applying the truths and the principles of Scripture. We can know what they are. We do know what they are. We can play dumb. We can say that Scripture is silent. We can say that an application will exceed what is written. But we really can know and do know and are responsible for the application.