It is astounding to me the lengths to which Christians will go to justify a blatant refusal to obey God rather than man.
In the 1960s, when I was a child growing up in the Southern Baptist church I was taught that there were ten (10) commandments that governed the conduct of God's people in all ages. The day that was observed as the Sabbath was Sunday. No one ever questioned the correctness of this that I can recall. I distinctly remember certain activities and duties being prohibited or curtailed on Sunday. I never heard the term "legalism" used in connection to this situation. It was always stressed that Christ and Him crucified was the only means of salvation, but this was never presented as a reason to disregard the duty of commandment-keeping.
Years later, when I became an adult and it occurred to me that my children were coming of age to benefit from spiritual guidance in the form of corporate worship, I lived in a location where Southern Baptists had virtually no presence. I discovered, while looking for a suitable alternative, that the fourth commandment was regarded lightly, if at all. Surprisingly enough, I was often told that the entire ten commandments were nailed to the cross. I found this shocking and even depressing as a prospect for guiding my children's morality.
The only church I could find that regarded the ten commandments seriously was the Seventh-day Adventist Church. This was also problematic because they seemed to be resting and worshipping on the wrong day of the week. I remembered my grandmother telling me that Adventists were Christians who worshipped on Saturday and didn't believe in Santa Claus (lol). After talking to some of these folks, I discovered that not only did the Bible definitely testify to the validity of the 7th day as the Sabbath rather than the 1st, but that in dozens of languages around the world, the actual word for the 7th day of the week was some form of the word "Sabbath," as in "Sábado" in Spanish.
The more I studied about the church, the more I realized how serious they were about being faithful to the testimony of the Bible as a whole. I found a truly comprehensive and systematic Theology that has for decades, helped me to know Christ in a personal and profound way that I never thought possible.
I anticipate many prooftexts, opinions, and insults to serve the purpose of dismantling my testimony and that's okay. I probably won't respond to many of those. But I'm always open to sincere inquiries.
***Absolutely nothing of what I'm about to say should be construed as calling into question the motive(s) of any individual--especially the OP.***
I thought it might be a good idea to begin with a brief personal testimony to lead into the topic of
the seal of God vs. the mark of the beast which is what we're really talking about here. Seventh-day Adventists are not known for their brevity when answering doctrinal challenges. And folks who enjoy challenging are good at keeping the questions very brief to give the impression that only a short answer could be acceptable. Obviously, I reject such a notion. The Bible contains over 3/4 million words. Alas, most folks are content to familiarize themselves with a minute fraction of them. Quite surprising when the Bible says that we should live by
every word.
The following video gives one of the best presentations on this topic I've ever heard. It runs for an hour, but the actual Bible study portion doesn't begin until the 15:30 point. The speaker is an experienced school teacher and a worldwide missionary and lecturer. He speaks very plainly and very rarely resorts to original language evidence. If a person sincerely desires to hear a clear answer to the question raised by the OP, they could definitely find a worse place to start than this video. I hope that those who chose to view it find it a pleasant, if not agreeable experience.