VEHSHAMRU BENAI YISRAEL
AND THE CHILDREN OF YISRAEL SHALL KEEP

The Yisraelite are to observe the Shabbat Celebrating it for the generations to come as an everlasting covenant. It will be a sign between Me and the Yisraelite forever. For in six days HaShem (Adonai) made the heavens and the earth, And on the seventh day He abstained from work and rested.

From Yeshayahu 66:23

And it shall come to pass that from one new moon to another and from one Shabbat to another, All flesh shall come to worship before me, says HaShem (Adonai)