One of the principal reasons given for sabbath observance is the preservation of the distinction between Israel and the nations of the world, in order that those self-same nations will be able to recognize in Israel the
mamlecheth kohanim vëgoy qadosh -- the “kingdom of
kohanim and holy nation” ( XIX, 6) -- from whom they are to learn fundamental morality:
V ë’atta dabbér el bënei Yisra’él lémor, Ach eth shabbëthothai rishmoru, ki oth hi’ beini uveineichem lëdorotheichem lada‘ath ki Ani Ha-Shem mëqaddishchem.
And you [Moshe], speak to the
bënei Yisra’él to say, Just you should keep My sabbaths, for it is a sign between Me and you for your generations to know that I, Ha-Shem, sanctify you (XXXI, 13).
Rashi elucidates:
It is a great sign between us that I have chosen you by granting you My day of rest for repose, so that the nations should know thereby that I, Ha-Shem sanctify you.
The other (not unrelated) reason is summarized in the Decalogue, where we find:
Ki shésheth yamim ‘asa Ha-Shem eth hashamayim vë’eth ha’aretz, eth hayam vë’eth kol asher bam, vayanach bayom hashëvi‘i, ‘al kén bérach Ha-Shem eth yom habshabbath vayëqaddëshéhu.
For [in] six days Ha-Shem made the heavens and the Earth, the sea and everything in them, and rested on the seventh day; therefore Ha-Shem blessed the sabbath day and sanctified it (ibid., XX, 11).
In other words, our observance proclaims the existence of the Creator, Who created the entire universe.
In light of this dual purpose in observing the sabbath, it is a little startling to encounter the following in the Talmud:
This Week's Torah Portion: The Importance of Shabbat
