One star-it is day. Two-twilight. Three-night. Rabbi Yose said, "Not large stars that we see in the day, nor small stars that we only see at night, rather medium stars . . . "
Rava said to his beadle, "You all, who do not have a grasp on Rabbinic measurement [of time], should light the [Shabbat] lamp while the sun is at the treetops."
When does Shabbat begin? When does it end? What separates the mundane time of the week from the transcendent time of Shabbat? The simple answer is that Shabbat is the seventh day of the week. Since Genesis 1 places the night before the morning ("And there was evening, and there was morning . . . "), Shabbat begins at nightfall on Friday. But how do we define nightfall? When the sun sets? When it gets dark? When the stars come out? The first part of our source states that it is only certainly night when three medium-size stars can be seen in the sky. Shabbat, therefore, ends only when the first day of the week has certainly begun, on Saturday night after the appearance of these stars. Twilight, however, is an odd time. It may be day, it may be night, and our Sages were unsure which it was. Thus Rava instructs his beadle to light the lamp inaugurating Shabbat before twilight on Friday, as is our practice today, just prior to sunset. This period of indeterminate time, from just before sunset until just after the appearance of three medium-size stars, varies in the mid-Atlantic region from approximately forty-five to seventy-five minutes over the course of the year. The result is that Shabbat is usually a twenty-five-hour affair, rather than a twenty-four-hour one.
As we move into Tishrei, the seventh month of the Hebrew calendar, the month that begins the liturgical cycle of the year, we should keep in mind that this period of transition is one that is also fraught with doubt. Rosh Hashanah inaugurates this period, just as the indeterminate period of twilight inaugurates the Shabbat. We are uncertain about our fate in the coming year and conscious of our need for forgiveness. As we move into the twilight of the year, we hope to see the stars of our redemption before the end of the High Holidays. May we all be written in the Book of Life for blessing, abundance, and peace.