"All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, thoroughly furnished unto all good works (Second Timothy 3:16-17).
And before anyone gets all hyper, it does not say that only the bible should be used. It just says that God is the author of the bible! What other reason would you need?
Now is when you step up and show me this other source you seem to believe should be used in conjunction with the bible. And, by the way, please include some reference to it being the infallible word of God.