The Sabbath or seventh-day of the week is a reminder of the law. We are saved by grace. The law came by Moses, but grace came through our Lord Jesus Christ. John 1:17
Christ rose on the first day of the week. That speaks of resurrection.
The Sabbath speaks of rest. We rest in the Finished Work of the Lord Jesus Christ on the cross. Jesus Christ is our Sabbath-rest. Matt 11:28-29. The Sabbath is not just a day of the week. It is a Person.
In the Middle East, Friday is the weekly holiday. Many Christians gather for rest and worship on that day. They cannot gather for worship on Sunday, which is a working day.
The Seventh Day Adventists keep insisting on the sanctity of the seventh day Sabbath, not realizing that the Sabbath has been fulfilled in Christ and His Finished Work.