Sabbatarian cult: Example: the Seventh Day Adventists.
Christians observe the first day of the week to worship the Lord Jesus. They recognize the importance of the resurrection, and the age of grace.
SDAs observe the seventh day of the week as a day of rest and worship. They continue to cling to the OT law, they continue to cling to legalism.
But we have been delivered from the law, and we live by GRACE.