From studying history, the Catechism, Popes writings etc., it seems to me that not a single teaching of the Catholic Church comes from scripture.
Jesus is the fulfillment of revelation. In Him God has said EVERYTHING.
Therefore Moses, David, the Prophets, etc. were only to forshadow what was made complete in Jesus.
Thus the Church does not claim that the in the bible God has said everything, but in Jesus God has said everything.
Jesus taught EVERYTHING to His apostles.
The apostles did not learn the Gospel from scripture, but directly from God, from Jesus Himself.
Mr 4:34 “He did not speak to them without a parable, but privately to his own disciples he explained everything.”
John 15:15 “for everything that I learned from my Father I have made known to you.”
John 14:26 “But the Counselor, the Holy Spirit, whom the Father will send in my name, he will teach you all things, and bring to your remembrance all that I have said to you.”
[size=3]Since Jesus revealed EVERYTHING to His apostles and sent the Holy Spirit to teach (explain) this revelation to the apostles
[size=3]then the apostles knew everything in regards to salvation.[/size]
[size=3]There is no teaching of scripture in the Old testament, and there is no teaching of scripture in the New Testament that adds to what the apostles learned from Jesus and the Holy Spirit.[/size]
The apostles could not have learned any additional teachings when the New Testament was written, because that would have made Jesus a liar. If Jesus taught them everything, then there is no other doctrine they could learn from scripture.
The apostles handed down this full and living Gospel to their successors, the bishops of the Church.
The Catechism teaches.
[size=2]This living transmission, accomplished in the Holy Spirit, is called Tradition, since it is distinct from Sacred Scripture, though closely connected to it. Through Tradition, "the Church, in her doctrine, life and worship, perpetuates and transmits to every generation all that she herself is, all that she believes."[/size]
Therefore since everything Jesus taught the apostles was handed down in Tradition TO EVERY GENERATION and this Tradition contains all the Church believes, then no teaching was “lost”, none was forgotten"
Therefore all doctrines that God has revealed have come through Jesus, who taught all to His apostles, who handed them all down in Tradition.
My personal conclusion is from this is that not a single teaching of the Catholic Church, and not a single teaching of the Gospel, which is the source of all saving truth, comes from the bible.
Later when the New Testament was written, certain parts of these teachings were written down in the form of salvation history. But, the Church knew every single teaching before a single word of the New Testament was written down.
Thus, to learn the Gospel, we must first learn these teachings the apostles handed down in Tradition, since these teachings are the word of God.
Since everything the Church believes is handed down in Tradition, then we must interpret scripture to conform to the Word of God handed down in this Tradition.
The apostles, and their successors, handed down this Tradition by their example, ways of worship etc, and by using words. They taught by organizing the Gospel they taught by teaching the articles of the Creed, Sacraments, Commandments and prayer.
Thus, the Catechisms, are simply a summary of the Gospel the apostles taught and preached.
Thus, the difference between Catholicism and Protestantism is that Catholics learned their teachings directly from Jesus, from God himself.
Protestants try to learn their teachings from salvation history, (Scripture), which is NOT the original source of the Gospel nor the fullness of revelation. That is why they fail so often.