Sunday served as “a sabbath” in Christendom since it was identified as the Lord’s Day in gospel times. Saying “a sabbath” not “the sabbath” since a Saturday sabbath wasn’t obligatory upon gentile Christians. It commemorated the raising of Christ from His physical human death which is documented by the gospels as happening on a Sunday morning.
There are oversimplifications bouncing around such as an accusation that the Roman church “moved the sabbath.” I’m one of those wascally Protestants, but even with Rome, nothing moved. A gentile membership did not observe Saturday (it was not required to) and a new special meaning of Sunday was accepted.
**Sunday served as “a sabbath” in Christendom since it was identified as the Lord’s Day in gospel times. **
To celebrate the Day of the Lord’s Resurrection.