Matthew 2: 23: And he went and dwelt in a city called Nazareth, that what was spoken by the prophets might be fulfilled, "He shall be called a Nazarene."
Please find that in the Old Testament for me since it appears in Matthew. You will soon see that it is not in Scripture but was passed down orally.
You might also indicate where Matthew 23: 1-3 appears in the Old Testament regarding Moses' seat.
I think you'll find that both these passages are not found in Scripture, and are examples of "Oral Tradition" (not written). This is why "sola scriptura" cannot suffice.
See Dave Armstrong, a Catholic apologist, for a great many more examples.
http://ic.net/~erasmus/RAZHOME.HTM
Except for the fact (believe it or not) that Protestants believe that Matthew is Scripture. So we're ok there.