[Esaias]

About a sign between God and Israel. Brother Blume, are you part of the commonwealth of Israel? Or not?

Anyways, the fact that the Sabbath was a sign between God and Israel does not mean "therefore nobody else ought to remember the Sabbath day to keep it holy." The Sabbath was a token or sign or indicator of the fact that Israel belonged to God. So the nations who did NOT keep Sabbath were thereby identified as not belonging to God. All this is just proving that non Sabbath keepers aren't in possession of one of the signs of being the Israel of God. Which I don't think was your intention in this line of reasoning, but, there it is.

The Sabbath, as well as the Feasts, were a sign, something that signified who was the God of Israel and who Jehovah's people were. It was a token of covenant relationship. Arguing from that to "therefore non Israelites have no obligation to obey the 4th commandment" is beyond reaching, it's just making a claim without any actual argumentation.