For Christians, Sabbath observance is disputable (Romans 14:5-6, Colossians 2:16-17). NT does not bind Sunday rest as law. The principle of rest is valuable; the specific day requirement is not binding. 70/100 Spiritually Safe.
The Sabbath commandment (Exodus 20:8-11) instructed Israel to cease work on the seventh day (Saturday) as a sign of their covenant with God. The New Testament treats the Sabbath differently. Colossians 2:16-17: "Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day. These are a shadow of the things that were to come; the reality, however, is found in Christ." Romans 14:5-6: "One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind."
While the specific Sabbath day requirement is not binding under the new covenant, the principle behind it is. Humans need rest — this is built into creation. Hebrews 4:9-11 speaks of a Sabbath rest for God's people, now fulfilled in Christ. Christians who work seven days without rest are violating the creation rhythm God built into human flourishing, even if not violating the specific Mosaic Sabbath law.
Working on Sunday is not a sin. Christians are free to work any day (Romans 14:5-6). The wisdom is to build rest and worship into your weekly rhythm — not because Sunday is sacred but because humans need rest and God's people need communal worship. Christians who work Sundays should find another regular time for corporate worship and personal rest. See our Is It a Sin? hub.
For a thorough treatment: GotQuestions on the Sabbath.
Questions about sin fall into two categories: things explicitly called sin in Scripture, and disputable matters (Romans 14-15) where Christians with different convictions should respect each other's consciences. Even when something isn't explicitly sinful: Does this practice reflect Christ's lordship over all of life (Colossians 3:17)? Is it beneficial — not just permissible? (1 Corinthians 10:23). Score: 70/100 Spiritually Safe.
See our Is It a Sin? hub. GotQuestions and the Gospel Coalition provide thorough evangelical analysis.