The Orthodox Christian Church adheres to the Nicene Creed. The Creed summarizes the faith in 12 articles, with utmost simplicity and clarity, so that every Christian can understand it and be able to express it accurately to others, both in the context of worship, and in everyday conversation. The Creed was developed by the first two Ecumenical Synods (World Councils). The first Council was held in Nicaea in 325 AD and developed the first 7 articles of the Creed. The second Council was held in Constantinople in 381 AD and developed the last 5 articles of the Creed, confirmed the first 7 articles, and finalized the document. Read more about Nicene Creed.
The Orthodox Christian Church uses as Holy Scripture the New Testament and the Old Testament (Bible). Specifically the Orthodox Church uses the New Testament version that is based on a large body of ancient manuscripts written in Greek, which are collectively known as “Textus Receptus” or Received Text. This is the same Greek text on which the King James Version of New Testament is based.
As its official Old Testament text, the Orthodox Christian Church uses the Septuagint. The Septuagint is the Greek-language Bible that the Jews used at the time of Jesus Christ. This translation had been in use for over two centuries before Christ, by the large portion of the Jewish population that lived outside their ancestral land, especially in cities around the eastern Mediterranean basin. Those people spoke Greek more comfortably than they spoke Hebrew or Aramaic. Since Greek was a universal language of culture and trade at that time, similar to what English is today, the Jews continued to use the Septuagint well into the 4th century after Christ. Since it was precisely in those Greek-speaking lands that Christianity first flourished, it was natural for the Church to adopt that text as official Holy Scripture.
Because the Orthodox Church makes it a point to not change anything, neither by innovating, nor by chasing popular trends, or by giving-in to political pressures, She has adhered to these texts solidly to this day. Read more about how the Orthodox Church views Holy Scripture.
Teaching was primarily oral in ancient times. Even though reading Scripture was an essential practice in Judaism, the teaching by the rabbis was mostly oral, due to the impracticality of producing books in those days.
Jesus Christ’s teaching was purely oral. True, they did read from scripture, but there is no mention anywhere that Jesus Himself wrote a book or that He requested any of His disciples to do so.
Moreover, when He gave his last few instructions to the Disciples to reach out to all the people, He still did not ask them to write books or establish academies.
Therefore, on one hand there existed a primarily oral tradition in Judaism, on the other Jesus continued that tradition during His ministry, and finally the Apostles simply continued it further.
Now, as need arose under specific circumstances to write a letter or a book, the Apostles certainly did write, in order to meet the specific demands. However, writing never became their primary preoccupation.
The Apostles went on to establish churches and ordained bishops to oversee those churches. The ordination was practiced ceremonially right from the start, by the laying of hand on forehead. As more need arose for written communication, the Apostles and their successors responded accordingly. Thus by the third century AD, enough literature had accumulated to prompt one to compile it systematically. Origen was among the first to do so. The Council of Laodicea in 363 AD and the Third Council of Carthage in 397 AD decided on what books to be included in the official Scripture. In deciding what books to include, they asked themselves the following simple and natural questions: Which books does the entire body of the Church hold most preciously? Which ones are indisputably authentic? Which authors are held in highest esteem? Which books are read during Eucharist as a universal practice? The answers to these questions came spontaneously out of the tradition that had grown by then.
Therefore, the Scripture was a product of the Church’s tradition. What makes the Holy Scripture holy is the holiness of the Tradition of the Church. Holy Scripture would not have existed in the form in which we know it, were it not for Holy Tradition. For this simple, natural and unbiased reason, the Orthodox Church holds Holy Tradition in the same high esteem as Holy Scripture. See also the following statements by Paul: 1 CORINTHIANS 11:2 and 2 THESSALONIANS 2:15.
Tradition, of course, is not only what went from mouth to mouth. Tradition also includes a host of written sources other than the canonized texts of the Holy Scripture. Most prominent among them are works by learned men of the 4th and 5th centuries, who are known collectively as the Great Fathers of the Church. These works include commentary on the Scriptures, elaboration on many obscure passages from the Bible, instructions for the organization of the Church, instruction on matters of worship, instructions on what a Christian should practice on an every-day basis, and much more. In this respect, these works are simply a continuation of a tradition that came straight from Judaism. Beside the Bible, the Jews continuously developed other secondary works that served many of the same purposes (Mishna etc.).
Other written sources of Holy Tradition include the decisions of the various Councils, biographies of Saints, more commonly known as Lives of the Saints, and works by elders (monks and nuns) on spiritual growth in Christ.