There are some who erroneously claim that Sacred Scripture alone is sufficient for understanding the Faith. As Catholics, we believe Sacred Tradition and Sacred Scripture are both necessary for a fruitful discernment of the Word of God because they together form the Deposit of Faith. Sacred or Apostolic Tradition consists of the teachings that the apostles passed on orally and through practice. These teachings largely overlap with those contained in Sacred Scripture, but the mode of their transmission is different. Sacred Scripture is a subset of Sacred Tradition put to writing. Together with the interpretive authority found in the Church, our Sacred Tradition provides a necessary context for discerning the proper meaning of Sacred Scripture. There are currently 36,000 different Christian sects and growing. This is largely because they lack the light of Sacred Tradition under the interpretive authority of the Catholic Church when discerning the meaning of Sacred Scripture.

"Sacred Tradition and Sacred Scripture, then, are bound closely together, and communicate one with the other. For both of them, flowing out from the same divine well-spring, come together in some fashion to form one thing, and move towards the same goal." Each of them makes present and fruitful in the Church the mystery of Christ, who promised to remain with his own "always, to the close of the age".
- Catechism of the Catholic Church, 2nd ed., (1997), n.80
As a result the Church, to whom the transmission and interpretation of Revelation is entrusted, "does not derive her certainty about all revealed truths from the holy Scriptures alone. Both Scripture and Tradition must be accepted and honored with equal sentiments of devotion and reverence."
- Catechism of the Catholic Church, 2nd ed., (1997), n.82
The Tradition here in question comes from the apostles and hands on what they received from Jesus' teaching and example and what they learned from the Holy Spirit. The first generation of Christians did not yet have a written New Testament, and the New Testament itself demonstrates the process of living Tradition.
- Catechism of the Catholic Church, 2nd ed., (1997), n.83

Mt. 2:23 - The prophecy "He shall be a Nazarene" is oral tradition. It is not found in the Old Testament.

Acts. 20:35 - Paul uses oral tradition to cite Jesus saying “it is better to receive than to give”. It’s not found in the Gospels.

2 Thess. 2:15; 2 Thess. 3:6 - Under the new covenant, Paul instructs the Church to hold fast to the traditions they were taught.

1 Cor. 11:2 – Paul tells the Church to hold fast to the traditions which God handed down to them from the apostles.

3 Jn. 1:13 - John emphasizes his preference for oral tradition even though he was a skilled writer.

Jn. 21:25 – John says everything could not be written in scripture. Therefore the rest was transmitted orally.

Tradition & Fathers
"Whenever anyone came my way, who had been a follower of my seniors, I would ask for the accounts of our seniors: What did Andrew or Peter say? Or Phillip or Thomas or James or John or Matthew, or any of the Lord’s disciples? I also asked: What did Aristion and John the Presbyter, disciples of the Lord say. For, as I see it, it is not so much from books as from the living and permanent voice that I must draw profit."
- St. Papias of Hierapolis, Sayings of the Lord (A.D. 115-140)
"The apostles at that time first preached the Gospel but later by the will of God, they delivered it to us in the Scriptures…"
- St. Irenaeus of Lyons, Against Heresies (A.D. 130-202)
"We do not take our scriptural teaching from the parables but we interpret the parables according to our teaching."
- Tertullian of Carthage, On Purity (A.D. 200)
"But they, safeguarding the true tradition of the blessed teaching, which comes straight from the Apostles Peter, James, John and Paul and transmitted from father to son have come down to us with the help of God to deposit in us those ancestral and apostolic seeds."