Numbers play a significant, if usually symbolic, role in Jewish thought. Perhaps the most symbolic number is seven, representing completeness; the most obvious example is Shabbat, the highlight that completes the week. Even our new year, Rosh Hashanah, takes place in the seventh month, and the holidays of Pesach and Sukkot are meant to be seven days long. Shavuot, the culmination of the exodus, is celebrated after seven weeks of seven days. The...

It is the holiday of Pesach that celebrates our becoming a nation and is the cornerstone of Judaism. Remembering the Exodus provides the backdrop to so many of our mitzvoth, whether it is Shabbat or Yom Tov, tefillin, mezuzah, kindness to strangers, or our sexual ethics. On Pesach, we focus on the meaning of freedom; but the mitzvah to remember the Exodus, zechirat yetziat mitzraim, is one that must be fulfilled each and every day, if by nothing...