Just thinking out loud here. Reformed say we can only worship God in the way he prescribes in his word. Obviously, this does not mean the Old Testament primarily, since the parts of the Old Testament that actually prescribe how to worship God are the very parts that are fulfilled in Christ!
So does it mean the New Testament? Presumably, but here is where we run into some difficulties. The New Testament was not written for much of the “apostolic church,” so they had no clear guidelines on how to worship God. After the final dating of the New Testament (circa 100 a.d.), it would still be a few centuries before anything remotely resembling a canon is given to the Church–so it seems there is no clear guideline on how to worship God from Scripture alone.
Maybe we are looking at it backwards. If we say that we take our worship from Scripture alone, and that this worship and this worship alone is God-pleasing, we have to conclude that the apostolic church worshiped God in a manner displeasing to him.
On the other hand, what if we took our canon from our liturgy? My friend Jay Dyer has collected a number of helpful articles on this point (and the following quotations of evangelical scholars are from Jay’s page).
F.F. Bruce writes in his classic The New Testament Documents: Are They Reliable? As follows:
“Another very important class of witnesses to the text of the New Testament are the Ancient Versions in other languages, the oldest of which is the Old Syriac and the Old Latin, go back to the latter half of the second century. Valuable help can also be derived from early Church Lectionaries.” (pg. 19)
Is the canon being formed in the context of liturgy? It appears so.
Anglican Scholar, Bishop Westcott (of the Westcott-Hort Text fame), in his older, The New Testament Canon:
“Words and rites [Liturgy] thus possess a weight and authority quite distinct from the casual references or deliberate judgments of individuals, so far as they convey the judgment of the many….It will be reasonable to conclude that the coincidence [of Scripture and Liturgy] implies a common source: that the written books and the traditional words equally represent the general sum of essential Apostolic teaching: and in proportion as the correspondences are more subtle and intricate, this proof of the authenticity of our books will be more convincing.” (pg. 13)
The formation of the canon of Scripture cannot be separated from the practice of the liturgy. Whatever else this means, it makes the claim that one’s way of worship–it’s liturgy–must come from the Bible very strained.