The Sabbath day was the Seventh Day ("Saturday") from the beginning until the reurrection of Christ. From then onward, Christians gather for rest/worship "on the first day of the week," commemorating his resurrection (and the eternal rest he won for us).

There are some deep theological reasons for this...e.g., prior to Christ man was to pattern his day/week/life according to the One in whose image he was made--"for in six days, the Lord created...and on the seventh, he rested." The pattern was to be obedient work and then enjoy an earned rest.

But--we've all heard the story--Adam, the first man, failed. As did all who descended from him (by ordinary generation).

Christ, the "second man" and "last Adam" succeeded where the first Adam failed.

Christians _start_ with rest, and then work--not to earn heaven, but to express gratitude for heaven already won and promised, by Jesus.

**cough**

...so...uh, yeah, Sunday first, please. 😅