Here is a good explanation of what is and is not sola scriptura.
First of all, it is not a claim that the Bible contains all knowledge. The Bible is not exhaustive in every detail. John 21:25 speaks to the fact that there are many things that Jesus said and did that are not recorded in John, or in fact in any book in the world because the whole books of the world could not contain it. But the Bible does not have to be exhaustive to function as the sole rule of faith for the Church. We do not need to know the color of Thomas' eyes. We do not need to know the menu of each meal of the Apostolic band for the Scriptures to function as the sole rule of faith for the Church.
Secondly, it is not a denial of the Church's authority to teach God's truth. I Timothy 3:15 describes the Church as "the pillar and foundation of the truth." The truth is in Jesus Christ and in His Word. The Church teaches truth and calls men to Christ and, in so doing, functions as the pillar and foundation thereof. The Church does not add revelation or rule over Scripture. The Church being the bride of Christ, listens to the Word of Christ, which is found in God-breathed Scripture.
Thirdly, it is not a denial that God's Word has been spoken. Apostolic preaching was authoritative in and of itself. Yet, the Apostles proved their message from Scripture, as we see in Acts 17:2, and 18:28, and John commended those in Ephesus for testing those who claimed to be Apostles, Revelation 2:2. The Apostles were not afraid to demonstrate the consistency between their teaching and the Old Testament.
And, finally, sola scriptura is not a denial of the role of the Holy Spirit in guiding and enlightening the Church.
What then is sola scriptura?
The doctrine of sola scriptura, simply stated, is that the Scriptures and the Scriptures alone are sufficient to function as the regula fide, the "rule of faith" for the Church. All that one must believe to be a Christian is found in Scripture and in no other source. That which is not found in Scripture is not binding upon the Christian conscience. To be more specific, I provide the following definition:
The Bible claims to be the sole and sufficient rule of faith for the Christian Church. The Scriptures are not in need of any supplement. Their authority comes from their nature as God-breathed revelation. Their authority is not dependent upon man, Church or council. The Scriptures are self-consistent, self-interpreting, and self-authenticating. The Christian Church looks at the Scriptures as the only and sufficient rule of faith and the Church is always subject to the Word, and is constantly reformed thereby
http://vintage.aomin.org/SANTRAN.html
Jesus never drank strong drink and He didn’t create 150 gallons of rotten juice to throw a drunken party. Jesus Christ never created anything tainted, and fermented juice is tainted. What He created was good and pure — not purtrid and corrupt! It’s down right blasphemous to suggest such a thing.?
“The Bible claims to be the sole and sufficient rule of faith for the Christian Church. The Scriptures are not in need of any supplement. Their authority comes from their nature as God-breathed revelation. Their authority is not dependent upon man, Church or council. The Scriptures are self-consistent, self-interpreting, and self-authenticating. The Christian Church looks at the Scriptures as the only and sufficient rule of faith and the Church is always subject to the Word, and is constantly reformed thereby”
The Bible makes no such claim for itself. It states that everything in it is inspired by God and useful for teaching, for reproof, for correction and for training in righteousness, but it does not claim to be the only rule of faith.
You admit that the Bible does not contain all knowledge, admit that Jesus himself said there was more he needed to say, admit that the Bible need not be exhaustive and then give as examples of information not contained therein as what color St. Thomas’ eyes were and what they ate?
Do you, in good faith, compare the words and teachings of Jesus with the mundane details of the life of the Apostles?
You further admit that the Church has teaching authority under the guidance and inspiration of the Holy Spirit, yet fail to name or define the Church. The nebulous “Christian Church” as Protestants call it, is not authoritative as we can clearly see by the variety of differing sects within that church. Jesus prayed for unity, one faith, one baptism.
Now, there is a claim that all Protestants share core beliefs, but as we sometimes see here that is not the case.
You further admit that oral teaching was a means of communicating the faith. The Apostles did indeed use Scripture, but they used it to prove who Jesus was. Why did they need to do that? To buttress their own authority. It was that closeness to Jesus of the Apostles that allowed them to have credibility and it is that same claim of closeness that the church demonstrates through its “Apostolic Succession” which gives it credibility.
The Church does not fear consistency between the Old and New Testaments. In fact, I submit that the Church is much more in tune with the belief that the New Testament is the fulfillment of the Old and that doctrines with which Protestants are in disagreement with the Church can be found within that fulfillment.