You realize that Apostolic era Christians were not assembling as Christians in Sysngogues, right?
That would have been a violation of Christ's command.
Additionally, religious Jews today nor at the time of the Apostles would have dared...
...To carry their collection (money) with them on the sabbath day.
...This is hard evidence Christians were assembling on the 1st day for worship.
...Exactly as Scripture and Secular history say they were.
Of course such command never existed, and Keith absolutely right
Above all, Jesus every Sabbath conducted His teaching in the synagogues, because there was no other place to do it, and sometimes together with His disciples.
Of course Jesus also teach under open air, and in many other places available, but He never missed the Sabbath Day.
And despite the fact that some of the leaders hate His teachings, the majority of the people were ecstatic to hear Him.
Luke 4.15
15.He began to teach
in their synagogues and was praised by everyone.
And this is very small example out of many when the people and even some of the leaders of the synagogues praised Jesus and have been astounded at His teaching.
Jesus teach not only in synagogues but even in the Temple, almost every day!
Luke 21.37-38
37.
Every day He was teaching in the Temple, and at night He would go out and spend the night on
the mount of Olives as it was called.
38.And all the people would get up early in the morning
to listen to Him in the Temple.
Home churches also have been established very quickly, and we know such examples from the Bible, but it took a long time until the churches purposely built as a place of Christian worship.
Church in NT literally means a place of gathering and does not mean the actual physical building as we know it today.
Actually in Antioch for the first time believers in Christ called as Christians.
Acts 11.25-26
25.Then Barnabas went to
Tarsus to look for Saul,
26.and when he had found him he brought him to
Antioch. So it was that for an entire year they met with
the church and taught a great many people, and it was in
Antioch that the disciples were
first called Christians.
There are two known Antiochs, one in Syria and another in Pisidia.
Antioch of Pisidia.
A city of southern Asia Minor in Phrygia, situated just north of the territory of Pisida. Antioch was an important first-century commercial center and an important center for the spread of the Gospel.
Founded by Seleucus I Nicator (about 300 B.C.) and named for his father Antiochus, it became a great center for commerce and was inhabited by many Jews.
The Apostle Paul preached in this city's synagogue and founded a church there during his first missionary journey (Acts 13.14-49). Just as Antioch exerted great cultural and political influence over the surrounding area, so also it became a strong base from which to launch the church evangelistic outreach (Acts 13.42-49).
In reaction to Paul's success, the Jews at Antioch caused some influential women to turn against the Gospel and had Paul driven out of the city (Acts 13.50).
(Nelson's Compact Bible Dictionary. Ronald F. Youngblood, F.F. Bruce, R.K. Harrison.)
At that time all the worship was conducted on the 7th Sabbath Day, as the Law of Moses required.
Until crooked, dishonest, and hypocritical "Christians" changed to Sunday, not the GOD.