"Only scripture is inspired 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
Did you notice anything funny about that verse from 2 Timothy? Read it again.
If you are a Protestant, you probably won't think that anything is wrong with it.
However, if you are Catholic you will know that (contrary to what Protestants think) the beginning of the verse as found in the Holy Scriptures of God says "All" instead of "Only."
That's right, all scripture is inspired by God for teaching and reproof, but not Only scripture!
"So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter."
-2 Thessalonians 2:15