14:1 Gather together on the Lord’s day, break bread and give thanks, having first confessed your sins so that your sacrifice may be pure.
The Lord’s Day was established as the first day of the week (Sunday) very early in the history of the church.
The weekly day of rest; the sabbath was never changed in the new testament. The apostles were always in the synagogue “on the sabbath.” Even the gentiles were joining them each week in the synagogues on the sabbath seeking correct teaching.