Exodus 20:8–11: Is Working on Sunday a Sin?
The fourth commandment binds Israel to cease work on the seventh day, and it grounds that rest in God's own pattern at creation. Because the text names neither Sunday nor the church's gathering, it cannot by itself answer whether working on Sunday is a sin.
Mark 2:23–28: Working on Sunday a Sin?
Mark 2:23–28 does not make Sunday work automatically sinful, and it does not treat the day as nothing. Jesus defends his hungry disciples by pointing to David's need and to God's purpose in giving the Sabbath, then claims authority over it as the Son of Man.