Exod 31:13 (NKJV) "Speak also to the children of Israel, saying: `Surely My Sabbaths you shall keep, for it [is] a sign between Me and you throughout your generations, that [you] may know that I [am] Yahweh who sanctifies you.
The Sabbath is a sign between Yahweh and His people forever. And not just Israel, but for all who enjoin themselves unto the blessings and promises of Israel by accepting Yahushua the Messiah.
Isai 56:3 (NKJV) Do not let the son of the foreigner Who has joined himself to Yahweh Speak, saying, "Yahweh has utterly separated me from His people"; Nor let the eunuch say, "Here I am, a dry tree." 4 For thus says Yahweh: "To the eunuchs who keep My Sabbaths, And choose what pleases Me, And hold fast My covenant, 5 Even to them I will give in My house And within My walls a place and a name Better than that of sons and daughters; I will give them an everlasting name That shall not be cut off. 6 "Also the sons of the foreigner Who join themselves to Yahweh, to serve Him, And to love the name of Yahweh, to be His servants--Everyone who keeps from defiling the Sabbath, And holds fast My covenant--
We know that not just Israel was to keep the Sabbath, but EVERYONE.
The Sabbath will also be kept when Yahushua returns:
Isai 66:22 (NKJV) "For as the new heavens and the new earth Which I will make shall remain before Me," says Yahweh, "So shall your descendants and your name remain. 23 And it shall come to pass [That] from one New Moon to another, And from one Sabbath to another, All flesh shall come to worship before Me," says Yahweh.