The Mosaic law applied only to the Jews. It was to keep them separate from the other nations as well as to point to the coming Messiah and prepare them as a nation to welcome Him. This event has passed and is no longer applicable.
The Ten Commandments has been in place from the beginning and will continue throughout eternity. Jesus' own Words "Think not that I am to destroy the Law, or the prophets: I am not come to destroy but to fulfill. For verily I say to you (Cronos), Till heaven and earth pass, one jot or tittle shall in NO WAY pass from the Law, till all be fulfilled
Look out side, Heaven and earth have not passed. They are still here.
Perhaps English is difficult for you -- I write "the ceremonial aspect of the old law—the Sabbath day itself"
The Sabbath day was the ceremonial aspect of the keeping the Lord's day holy
ceremonial, ceremonious, formal, conventional mean marked by attention to or adhering strictly to prescribed forms. ceremonial and ceremonious both imply strict attention to what is prescribed by custom or by ritual, but ceremonial applies to things that are associated with ceremonies
Col. 2:16-17 16 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. 17 These are a shadow of the things that were to come; the reality, however, is found in Christ.
This says it very clearly - for Christians, Sabbath days were a shadow foreshadowing the first coming of the Christ
For Christians, we now worship the Lord on the FIRST day of the New covenant