What is the significance of reciting kiddush on Shabbat? Is the friday night kiddush or the Shabbat day kiddush more important? Is the wine a biblical obligation or a rabbinic one? Is there a relationship between kiddush and havdalah?
The mitzvah to observe the Shabbat is repeated numerous times in the Torah. Most notably this is one of the Ten Commandments, which are repeated twice in the Torah, first in Parshat Yitro and again in Parshat Vaetchanan with several minor variations. One of the differences is that while in Parshat Yitro we are commanded to “remember” the Shabbat (zachor),1the verse in Parshat Vaetchanan commands us to “guard” the Shabbat (shamor).2 The Talmud explains that G‑d actually said both words, zachor and shamor, in one utterance.3
This double statement in a single utterance is understood to constitute two seperate commandments: The verse in Parshat Vaetchanan, which uses the word shamor—guard, requires us to abstain from various kinds of “work” (melachah) on Shabbat. The verse in Parshat Yitro, which uses the word zachor—remember, requires us to actively remember the holiness of Shabbat, and not merely desist from work activities.