I'm new to the orthodox faith, but this is how I respond to my Protestant friends. The New Testament does not go into much detail regarding the form of worship to be used. However, the New Testament does teach that there are important traditions passed on orally, not found in Scripture. (2 Thess 2:15, 1 Cor 11:2) All of the Apostles were Hebrew. They originally worshiped in the temple until they got kicked out. It is very safe to assume their worship was originally liturgical in nature because Hebrew worship was, and that is where we derive our own orthodox style.
This "safe assumption" is confirmed by holy tradition. The Fathers who convened at every Church council worshiped in this liturgical style. The liturgy has been accepted as the proper form of worship by the Church, it seems, from the very beginning. It seems to me that the liturgy is among the "traditions" Paul said were important to pass on beside Scripture. At times, the liturgy has been what kept orthodoxy alive in some areas, such as when corruption of the high-level hierarchy set in under the Turks after the fall of Constantinople.
One of the passages that confirmed the liturgy as "biblical" to me is 1 Tim 4:13 – "Until I come, devote yourself to 1) the public reading of Scripture, 2) to preaching and 3) to teaching." Because Scripture has always been 100,000 times more healing to my soul than any of even the best sermons I've heard, as a Protestant I always longed to hear more of it in church. Paul listed it first in 1 Tim 4:13, but my pastors words always seemed to outnumber the words of Scripture on Sundays. They preached and teached for 30 minutes but read Scripture for only one or two minutes.
I always wondered, "Why don't we publicly read it much any more?" My pastors said it was because now more people can read it on their own at home. I should have replied, "Ok, but how many in your congregation are actually reading much of their Bibles at home?" But I accepted their answers.
When I finally found orthodoxy I was overjoyed at the amount of Scripture in their services. The words of God's holy scriptures outnumbered even their own pastors' words in their Sunday services. Now that is a very humble posture to take before God's Word, and it seems Scriptural through and through (1 Tim 4:13). I no longer heard 30 minutes of opinion interspersed with 2 minutes of scripture reading. Between the hours, the liturgy, and the reading during the kissing of the cross, I heard a 5 minute sermon surrounded by nearly 30 minutes of Scripture reading. That didn't even count 30 minutes of song and prayer, much of which is word for word Scripture if you listen carefully.
I was wondering if anyone here could briefly, or not so briefly, explain to me the origin of our liturgical style of worship in terms of the New Testament and even Old Testament prophecies so that when my Protestant friends question it I will be better prepared to explain it. I know that the Eucharist originated in Acts and much of the Liturgy is based off of Old Testament prophecies and the book of Revelation, but, I do not know much about the details or specifics so I was wondering if someone here could explain this to me better, along with anything important in regards to the original Greek manuscripts of the New Testament, because I am aware that sometimes to get the full meaning we have to return to the Greek instead of taking it at face value like certain denominations do.