“Sacred Tradition and Sacred Scripture make up a single sacred deposit of the Word of God...” (DV 10)
My friend Al Kresta (Catholic talk show host and author) once noted that in C. S. Lewis' famous book, Mere Christianity: an ecumenical effort to find things that all Christians shared in common, and the “non-negotiables” of Christianity, a central, crucial doctrine of two of the three major divisions of Christianity was omitted.
The great Anglican apologist did not include a doctrine of the Church as a binding authority in the Christian life, which is a belief strongly held by Catholics and Orthodox, but formally denied by Protestants, who hold that only Scripture is an infallible authority (what is known as sola Scriptura; literally, “Bible Alone”).
As a Catholic convert, whose former biggest objection to Catholicism, by far, was the notion of an infallible Church or pope, I understand this viewpoint, but I thoroughly reject it now. I'd like to highlight three biblical passages that teach a very strong view of the authority of the Christian, or Catholic Church (contra sola Scriptura).
Matthew 16:18-19 And I tell you, you are Peter, and on this rock I will build my church, and the powers of death shall not prevail against it.  I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven.
This is also a key passage for the defense of the papacy, but that is a separate topic. Here I want to note that there is such a thing in the Bible as “the Church” and that it was established by Jesus Christ Himself, as His own Church. Some comedian once made a wisecrack about there being “only one the Church.” He spoke the truth.
St. Peter and the other apostles (of whom bishops and priests are successors) were given the power to bind and loose: Jewish rabbinical terms for penance (binding) and forgiveness extended by a representative of God (loosing). These decisions corresponded with the decrees or will of heaven itself (that is, God). Therefore, such power is indicative of a strong view of the authority of the Church.
The third notable element in this passage is the concept of the “powers of death” not being able to prevail against the Church. This means that the Church (not just individual Christians, but the collective entity) will always emerge victorious in its spiritual battles. The King James Version renders the phrase above as “gates of hell.” This brings to mind a great image of the Church breaking through; conquering the gates of hell itself and overcoming evil and Satan.
Acts 16:4 As they went on their way through the cities, they delivered to them for observance the decisions which had been reached by the apostles and elders who were at Jerusalem.
This verse is often overlooked in discussions about authority in Christianity. St. Paul didn't simply hand out Bibles, nor did he preach the gospel only on his evangelistic journeys. He also proclaimed an authoritative Church decision, made at the Jerusalem Council, which is described in Acts 15:1-30.
What happened there was not “Bible Alone” or individual Christians and the Holy Spirit, independent of other Christians, but very clearly a strong Church authority. The “apostles and elders” (15:6), representing the “whole church” (15:22) gathered, much as bishops in our time got together at the Second Vatican Council (1962-1965).
The main question they dealt with was whether Gentile Christian converts were required to be circumcised and to observe the entire Jewish Law. The Church in its council decided that it was not necessary, with the participants confidently proclaiming, “it has seemed good to the Holy Spirit and to us.” The Holy Spirit guided the process (cf. Jn 16:13).
St. Paul then went out and proclaimed what the council (himself included) had decided, to be observed as a binding decree. If that's not Church authority, it's difficult to imagine what would be. If God approved of such Church-wide decisions in the early Church, why not also today? Why would that cease? It makes no sense to argue that it all went away and that we were left to fend for ourselves as mere individuals.
1 Timothy 3:15 . . . the household of God, which is the church of the living God, the pillar and bulwark of the truth.
Truth is truth. It cannot be error, by its very essence and definition. Knowing what truth is, how can its own foundation or pillar or bulwark or ground, be something less than total truth (since truth itself contains no falsehoods, untruths, lies, or errors)? It cannot. It's impossible, as a straightforward matter of both logic and plain observation. A stream cannot rise above its source.
What is built upon a foundation cannot be greater than the foundation. If it were, the whole structure would collapse. If an elephant stood on the shoulders of a man, as its foundation, that foundation would collapse. The base of a skyscraper has to hold the weight above it. It can't be weaker than that which is built upon it. The foundations of a suspension bridge over a river have to be strong enough to hold up that bridge. They can't possibly be weaker than the bridge or else the structure would collapse.
Therefore, we must conclude that if the Church is the foundation of truth, the Church must be infallible, since truth is infallible, and the foundation cannot be less great and strong than that which is built upon it. Truth cannot be built upon any degree of error whatever because that would make the foundation weaker than the superstructure above it.
Accordingly, given the above biblical passages and many others, the Catholic “three-legged stool” rule of faith may be defined in the following way: In the biblical (and historic Catholic) view the inspired, infallible Bible is interpreted by an infallible, divinely guided Church, which in turn infallibly interprets and formulates the true doctrinal (apostolic) tradition.