Remember the Sabbath day, to keep it holy. Six days you shall labor and do all your work, but the seventh day is the Sabbath of the LORD your God. You shall not do any work, you nor your son, nor your daughter, your manservant, nor your maidservant, nor your cattle, nor your stranger within your gates. For in six days the LORD made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the LORD blessed the Sabbath day, and sanctified it.
The Suzerain cares about people all the way down to the lowest in His domain. The first and primary effect of declaring a holy day was to prevent the powerful from overworking their subordinates and dependents. This is fundamentally about mercy to the unfortunate.
We cannot find any external proof the ancient Hebrews kept the seven-day calendar continuously before the Period of Exile in Babylon. Other nations had similar patterns, but only Scripture indicates the practice is truly ancient. Given periods of apostasy, we have no basis for insisting it was continuous from the Garden. However, the moral basis is God’s personal practice. If Our Lord takes a break one day in seven, we have no reason to resist. He can surely dictate we observe His personal habits.
If all you get from this is the austere demand your life must stop on Saturday, then you have missed the point. I don’t really care which day of the week you choose, and I doubt God cares, since what we have today is a German adaptation of a Roman practice absorbed during the time of early Christian tolerance, which grew out of a sect of Judaism. Talmudic Jews are notorious for the most outrageous claims of mythical authority, and Jesus often poked holes in their pompous emptiness. They had turned the Law into a very oppressive weapon against the common folks, standing this command on its head.
The Son of Man was Lord of the Sabbath, and claimed the authority to interpret what it should have meant. With all the references to doing things on the first day of the week after His Ascension, and Paul’s discussion about holidays being of no real significance, we have no reason to be crabby about it. If you can’t meet your material needs in six days, you need too much, and you aren’t relying on God to provide. So we take one day in seven to celebrate the mercy of our Lord upon us, and we share the mercy with others.