One of the chief premises, if not THE chief premise, of Protestantism is sola scriptura, or the teaching that the Bible alone is the sole infallible rule of faith. The fatal flaw of that teaching is the teaching itself is not found in the Bible! By it's own standard the teaching of sola scriptura is fallible, and due to the fact that it is NOT taught in Scripture, we'd have to say it's inherently flawed.
Where is this teaching first found? Let's not be satisfied with references which speak to sufficiency - because sola scriptura is not about sufficiency - rather it is about "sola."