To put it plainly, our faith is the life of God himself shared with his creation. It is the same faith which was shared with all of our fathers in the faith, Abel, Enoch, Noah, Abraham, Isaac, Jacob, and all the prophets, apostles, martyrs, confessors, and ascetics throughout the ages. The Church as we know it today, of course, was not what all these righteous ones knew, but it was the same faith yet revealed in shadows. What we call the Divine Liturgy today with its "unbloody sacrifice" of the Lamb, was for our forefathers all the oblations and whole-burnt offerings which the Lord commanded.
Our faith then is the faith of all those that rightly glorified God, many of whom are listed in the Letter to the Hebrews; but to refer to an Orthodox Church was from the day of Pentecost forward. Yet, to call the Church "Orthodox" does not mean it is another denomination of Christianity. Again, to put things plainly, we are the Church of Jesus Christ, the original apostolic Church founded on Pentecost. Throughout the ages, many sadly broke away from the true Faith and the true Church, thus our ancestors described our Church with the adjective "orthodox" because we are right-glorifying Christians. While those that broke away sought to systematize and thus reduce the Faith merely into beliefs and practices, the right-glorifying Church always knew the proper substance of the faith is the worship or glorification of God. In other words, those that are right-glorifying are the ones that have faith.
The faith and worship given at first to our righteous ancestors were, so-to-speak, contained in a seed that was planted in their very lives. That planting of the revelation of faith and glorification of God, was cultivated by the action of the Holy Spirit, the Lord Himself in the lives of those righteous one who obeyed him, all the way to our present day. Thus, our Divine Liturgy, our faith and worship, today is the natural outcome of that divine cultivation and revelation through our ancestors in faith.
This is true because our worship and faith have never lost their instrinic connection to that seed which was planted long ago in our ancestors. That connection is defined in "offering" or "sacrifice." All the patriarchs and ancestors in the faith made their oblations and whole-burnt offerings, and we offer our "hearts" and our "thanks" in the Divine Liturgy. We also offer our prayers, candles, incense, fasting, and all our seemingly small and insignificant offerings to the Lord. Even what we do offer, it all comes from him, so we can only offer up what he has already given to us. But it is "offering" and "sacrifice" which is essential to the right glorication of God.