Mark 13:31
“Heaven and earth will pass away, but my words will not pass away.”
Passing tradition down orally leaves room for omission. Once the Bible was written, we had oral tradition converted to the written Word. To me, that’s more reliable than oral tradition.
He said “my words,” not “the Bible.” The Bible contains part of Christ’s words, as is stated specifically in the last chapter of St. John’s gospel:
John 21:25 (DRB) - “But there are also many other things which Jesus did; which, if they were written every one, the world itself, I think, would not be able to contain the books that should be written.”
The scriptures also tell us what is more reliable:
1 Timothy 3:15 (DRB) - “But if I tarry long, that thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth.” This does not say that the scriptures are the pillar and ground of truth, so it makes no sense to claim otherwise, regardless of what you personally believe to be more reliable.
Then how can the Church know that what they know about Christ is true? Particularly the stuff not written in the Bible? I, personally, see the Bible as a big history book linking us to the time of Christ (NT) and knowing what led up to His coming (OT).
Because scripture explains that this is left to the Church (1 Timothy 3:15 - see above), and he gave authority to Peter, including the power to bind and loose:
Matthew 16:18-19 (DRB) - “And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it. And I will give to thee the keys of the kingdom of heaven. And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose upon earth, it shall be loosed also in heaven.”
He also gave this charge to Peter:
John 21:17 (DRB) - “He said to him the third time: Simon, son of John, lovest thou me? Peter was grieved, because he had said to him the third time: Lovest thou me? And he said to him: Lord, thou knowest all things: thou knowest that I love thee. He said to him: Feed my sheep.”
He also has promised the Holy Spirit to the disciples:
John 14:26 (DRB) - “But the Paraclete, the Holy Ghost, whom the Father will send in my name, he will teach you all things, and bring all things to your mind, whatsoever I shall have said to you.”
And again:
John 16:13 (DRB) - “But when he, the Spirit of truth, is come, he will teach you all truth. For he shall not speak of himself; but what things soever he shall hear, he shall speak; and the things that are to come, he shall shew you.”
So honest, God-fearing, bible-studying Christians who are legitimately led by the Holy Spirit are in error?
Given that we all hold vastly different interpretations of the same holy scriptures, we can’t all be right!