By His own hand God wrote a table of law in stone - twice. If, as a key word, you follow the word "testimony" after Exodus 20 it becomes apparent that God is quite interested in and meticulous about that document. It was given a special place in the Tabernacle - He set His throne on it (Ex 25:16, 21-22; 40:20). That doesn't look like ceremony - it looks like the constitution of a government. The 7th-day sabbath is part of that constitution. Has God written a new constitution or was the life work, death, resurrection, and ascension of Jesus key to enabling us to live under the one He wrote? The other document describing other sabbaths (and those may be more justly classified "ceremonial") were written in Moses' handwriting under God's direction in a book and placed as a supplement "in the side of the ark of the covenant..." see Deut 31:24-26.