The Targum Pseudo-Jonathan grounds the Sabbath in cosmology. "For in six days the Lord created the heavens, and the earth, and the sea, and whatever is therein, and rested on the seventh day: therefore the Lord hath blessed the day of Shabbatha and sanctified it" (Exodus 20:11).
The Targum's Aramaic noun is Shabbatha, the feminine intensive form — the Sabbath as a living being, a queen, a bride. Later Jewish mysticism would elaborate this into the Shekinah descending at sundown on Friday, but the seed is already in the Targum's grammar: the day is not a date on the calendar but a presence that arrives.
And notice the sequence of creation the Targum lists: heavens, earth, sea, and whatever is therein. Three domains and one summary. The same triple geography that appears in the prohibition of idols — above, below, and in the waters. The Sabbath is God's claim over every zone. Resting from work is resting from every possible act of creation, in every possible realm.
Why is the seventh day both blessed and sanctified? The rabbis noticed that these are two different operations. Blessing means the day gives increase — the food tastes better, the sleep is deeper, blessings multiply. Sanctification means the day is set apart for a purpose, like a vessel reserved for the Temple. Every Sabbath is both a gift you receive and a gift you return.
The takeaway: to keep Shabbat is to replay, once a week, the last act of creation — the moment when God stopped making and simply was.