We find the Sabbath was given unto Israel for a sign between God and them. So you have it in Ezekiel 20:12 “I gave them My Sabbaths, to be a sign between Me and them, that they might know that I am the LORD that sanctify them.” By this they were distinguished from all other nations. These were a plain and evident proof that they were the Lord’s people, and that Jehovah was their God. This did loudly proclaim God’s choosing and calling them out from the rest of the world, and gracious setting them apart for Himself, as His peculiar portion and inheritance. And indeed, where there is no care of sanctifying the Sabbath by nations, families, or persons, it is a plain case, it amounts to a demonstration, that they are unsanctified nations, families, and persons.
– Rev. Samuel Slater, English Puritan Pastor