Christians are not under the law covenant, because Christ fulfilled that law when he died upon the torture stake. "For Christ is the end of the Law." (Rom. 10:4) There is no justification in the Scriptures for separating the Ten Commandments from the rest of the law covenant and claiming that it was not brought to an end by Jesus but is binding upon Christians.
The apostle Paul wrote at great length about the law covenant and how it was brought to an end, but not one word was said about the Ten Commandments as being a separate moral law that is eternally binding and the rest of the Law being a ceremonial law that ended.
At Romans 7:6 he speaks about Christians being "discharged from the Law," and in the next verse he refers to the tenth commandment without giving any indication that he considered it to be a separate law. Then in the thirteenth chapter of Romans he mentions several commandments in the Decalogue and points out that they are all fulfilled by the new commandment that Jesus gave to "love one another."Rom. 13:9, 10; John 13:34; Matt. 22:39, 40.It might also be noted that in the sermon on the mount Jesus quotes from the Ten Commandments as well as the rest of the Law without making any distinction between them.Matt. 5:21-44.
The fact that Jesus kept the sabbath does not mean he set the example for Christians to keep it. It was necessary for him to observe it because he was born under the law covenant, and until he fulfilled it by his sacrificial death he was obliged to keep all the Law. If Christians should keep the sabbath because he did, then they must also keep the entire Law as he did, and we know from the Scriptures that this is not required of Christians.