Recently someone — it might have been of one of our older kids — asked me why Jews both inaugurate the Sabbath over a cup of a wine (at Kiddush) and bid it farewell similarly, over a cup of wine (Havdalah). I found an answer over Shabbat in Rav Hirsch’s commentary on the Torah, in his explanation of the Fourth Commandment as recorded in Exodus. In the order of Biblical symbols, a cup alludes to our fate as meted out to us by God. Look here for a list of verses from the KJV version of the Hebrew Bible that use the word “cup”; you’ll see what I mean.
The medieval hymn Adon Olam describes God, the “Lord of the Universe,” as “my cup, my portion when I cry.” The essential point of the Sabbath is to acknowledge God as the guiding force behind creation and history. We receive our “cup” from Him. Hence the appropriateness of celebrating the Sabbath by lifting and receiving our cup, filled with beautiful wine. Per Jewish custom, there is a whole choreography to this.
We hope our portion from God will be as good, as gently intoxicating, as good wine. What an insult, really a blasphemy, to use sickly sweet grape juice or Manischewitz as some Jews do! Maimonides rules, in fact, that Kiddush may not be said over sugared or cooked — i.e., grossly inferior — wine (Hilchot Shabbat 29:14).