The dread Mysteries, full of such great salvation, which are celebrated at every Liturgy, are also called a Thanksgiving [Eucharistia] because they are the remembrance of many benefits, and they signify the culmination of God's Providence towards us, and in every way cause us to be thankful to Him.
Before the writing of the Holy Scriptures, that is, of the sacred texts of the Gospels, the Acts and the Epistles of the Apostles, and before they were spread to the churches of the world, the church was based on Sacred Tradition....The holy texts are in relation to Sacred Tradition what the part is to the whole.
The roof of any house stands upon the foundations and the rest of the structure. The foundations themselves are laid in order to carry the roof. This is both useful and necessary, for the roof cannot stand without the foundations and the foundations are absolutely useless without the roof-- no help to any living creature. In the same way the grace of God is preserved by the practice of the commandments, and the observance of these commandments is laid down like foundations through the gift of God. The grace of the Spirit cannot remain with us without the practice of the commandments, but the practice of the commandments is of no help or advantage to us without the grace of God.
Almsgiving heals the soul's incensive power; fasting withers sensual desire; prayer purifies the intellect and prepares it for contemplation of created beings. For the Lord has given us commandments which correspond to the powers of the soul.
Let us look after those who precede us into the other world, and do for them all that we can, remembering that Blessed are the merciful, for they shall obtain mercy.
Of the beliefs and public doctrines entrusted to the care of the Church, there are some which are based on Scriptural teaching, others which we have received handed down in mystery by the tradition of the Apostles; and in relation to the true religion they both have the same force.