Craig Keener has written a helpful article on Sabbath observance. If you’re not familiar with Dr. Keener, I consider him to be the top charismatic scholar in the world. He’s devout. He got his PhD from Duke, where I can’t imagine even getting into. His commentary on Acts runs in the thousands of pages. All that to say, take what he says very seriously.
The ideas in the quotes below are what finally persuaded me that Christians should keep the Sabbath (that was before I read this article).
As I tried to study the biblical text honestly, I could see that this was not just a matter of keeping laws designated for Israel; God actually modeled the Sabbath rest in creation (Gen 2:2-3). Whether we take that narrative literally or not, the principle of the Sabbath is there, and it apparently is an example for all people, not just those who are ethnically descended from Abraham.
…observing the Sabbath is one of Ten Commandments (Exod 20:8-11). We take all the other Ten Commandments as universal; why exclude this one? In the Prophets, God promises to welcome Gentiles into his covenant, provided that we observe his sabbaths (Isa 56:6-7).