Contrary to what most of us have been taught and have believed all of our lives, we're not really given instructions as to how we're to worship, either individually, or as a group. We've taught for years that there are rules for corporate worship, but we've had to inductively reason those rules out using (fallible, I might add) human logic. Such rules include meeting on the first day of the week, to break br.., er, have the Lord's Supper, and to conduct Five Acts of Worship (and no more, so I guess immersion is not an act of worship or we wouldn't be doing it in our assemblies, or maybe we've just miscounted and there are Six Acts of Worship). Yet when you really sit down and look at these "approved Apostolic examples" or necessary inferences, you realize they're not commands given by God, but they're commands deduced by men, taught as doctrine. I suspect the Teachers of the Law in Jesus' day used similar human logic to arrive at their traditions. Jesus strongly condemned them for elevating their human-derived conclusions to the level of Command (Matt 15:1-9).
God has given us very few actual commands about how to worship; most of
what we believe are God's Rules for Worship are actually rules we've
derived using human logic, and poor logic at that sometimes. For
example, are we 100% certain that Acts 20 implies a weekly gathering for
the purpose of taking the Lord's Supper? Maybe it was just a going-away
supper for Paul on the last night he planned to be there (having
intended to leave on the morrow). Maybe it was the Jewish Second
Passover for those who for whatever reason missed the first official
one; the timing is pretty close. Maybe it was a weekly event, but not
for the Lord's Supper, but just for an ordinary meal. Notice that if
Luke was using Greek reckoning, if the disciples met on the first day,
Paul didn't break bread until Monday, after midnight. If Luke was using
Jewish reckoning, the disciples met on what we would consider Saturday
night. Or maybe Paul's breaking bread after midnight wasn't the same as the breaking of
bread for the purpose of the meeting. The point is we make assumptions,
and then bind our conclusions as if they are God's commandments, when
God has not really given us many commandments.
In fact, Paul specifically contrasts the old covenant, having many rules
and regulations, with the new covenant, saying, "Why do you submit to
regulations: 'Don't handle, don't taste, don't touch'? .. They are
commands and doctrines of men, although they seem religiously valuable"
(Col 2:20ff), adding, "Don't let anyone judge you about what you eat or
drink, or what holy days you may or may not observe, including the
Sabbath" (v 16).
Is it not odd that God clearly spelled out his instructions for worship
under the old covenant, but then left it to the vagaries of human
reasoning to figure out his instructions for worship in the new covenant
based on hints and clues and a very few specifics? If how we "do"
worship was so important in the old covenant that God spelled out the
details, what does it say about how we "do" worship in the new covenant
that he hasn't spelled out the details?
Most of us have grown up thinking we have rules for our "worship
assembly", when in reality most of those rules are jigsaw-puzzled
together using human logic, rather than being commands given by God.
Thus, as Paul argues in Romans 14, perhaps we should be a little less dogmatic about how "worship service" must be conducted.