The Sabbath itself is not eternal, but was a sign of the Mosaic covenant. Exodus 31:13-17 designates the day as a “sign between Me and you throughout your generations.” As such, it is given to a specific people for a specific time to remind them of a specific covenant – the Mosaic one. When that covenant is replaced with a new one, the sign that pointed to it – the Sabbath – no longer applies. True, the “sign” is said to be “forever,” but…“forever” does not necessarily mean “eternal,” but forever until fulfilled. For example, various other elements of the Mosaic law were spoken of as permanent – including the administration of the tabernacle, animals sacrifices, and the priesthood. All these were fulfilled in Christ.