The apostles did indeed get together “on the first day of the week,” but that was Havdalah on what you would call Saturday evening.
All mention of gathering on the first day of the week in the NT is the Havdalah tradition.
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Can anyone point me to one verse in the NT that after Jesus rose from the dead, anyone:
1. was told to keep the Sabbath
2. that any Christian kept the 7th day sabbath.
just one??