The Church has always held fast to and taught the Sacred Traditions rooted in Scripture, handed down by the Apostles from the very beginning. The New Testament was not comprised by the Church until almost 400 years later. Therefore, it is false to believe that the Bible is the only teaching authority you need. Just witness the the disunity and disorder among the countless Protestant denominations without the teaching magisterium of the Church. In Thessalonians 2.15, Paul writes "Therefore, brothers, stand firm and hold fast to the traditions that you were taught, either by an oral statement or by letter of ours." The Bible came out of the Church, not the other way around.