Commentary for Leviticus 23:3

ששת ימים SIX DAYS [MAY WORK BE DONE BUT THE SEVENTH DAY IS THE SABBATH OF STRICT REST] — What relation is there between the Sabbath (the day that is invariably fixed by God as the holy day) and the festive seasons (the times of which are variable, being dependent upon the proclamation of the Sanhedrin)? But by putting both into juxtaposition Scripture intends to teach you that he who desecrates the festivals is regarded as though he had desecrated the Sabbath, and that he who keeps the festivals is regarded as though he had kept the Sabbath (Sifra, Emor, Section 9 7).

'שבת היא לה, He, the creator of light and darkness assigns these days in all your dwellings, wherever on earth. The reason this is spelled out is that we might have thought that just as days and nights are not constant, being longer in the summer than in the winter respectively, so that the hours of the first Sabbath in history might serve as the model for all future Sabbaths, and Jews over the world ought to observe the 24 hours which Jews in the land of Israel observe as their Sabbath. The Torah, by writing בכל מושבותיכם, indicates that the commencement and conclusion of the Sabbath depends on the local times of day and night, not on a central location. [as opposed to the determination of the monthly time when the new moon , i.e. the new month begins, which is related to its astronomical constellation in the sky over Jerusalem, which serves as the ”dateline” for the Jewish people.Ed.]

בכל מושבותיכם, “in all your dwellings.” The Sabbath laws apply regardless of whether you are in the Holy Land or in exile. Up to now the Torah had dealt with different kinds of vows made by people, resulting in those being offered as animal sacrifices on the altar in the Temple. On those days everybody is required to offer sacrifices in the Temple regardless of having vowed to do so or not. It also describes the type of work that must not be performed on these festivals.

Shabbos. The word שבת connotes rest, interrupting and refraining from work. In my opinion it also connotes intellectual analysis and exploration. This is based on the verses (Koheles 9:11), “I returned (שבתי) and saw under the sun,” and (Yirmiyahu 31:18) “For after my return (שובי) I have completely changed my mind.” These connote peace of mind (ישוב הדעת), as in the words of the Rabbis. This is because Shabbos is a special day for investigation and seeking in the affairs of Hashem, Blessed be He.