It is in chapter 1 of Tractate Kiddushin that we find the classic formulation of men’s and women’s responsibilities when it comes to mitzvot. As the mishna on Kiddushin 29a says, “With regard to all positive, time-bound mitzvot, men are obligated and women are exempt.” That is to say, anytime God commands us to perform a specific action at a specific time, only men are required to do it. If a mitzvah doesn’t have a time restriction, however, or if it is a negative commandment or prohibition, then men and women are equally obligated. This explains why, as we saw last week, both men and women must honor their parents—this a positive, non-time-bound commandment. Likewise, prohibitions on Shabbat labor or theft are binding on both sexes. But since a Jew only sleeps in a sukkah at the designated time during Sukkot, and only wears tefillin during the day, women do not have to perform these mitzvot.
.. It is in the course of this discussion that we come to the matter of women’s beards. The Bible commands that Jews are not permitted to “destroy the corners of your beard.” Exactly what this means is the subject of dispute in the Talmud—the consensus is that shaving is forbidden, but tweezing and trimming with a scissors is permitted. But there is no doubt that it is a prohibition and therefore should apply to men and women equally. Yet the Gemara says that women are not included in this prohibition. Why not?
The first answer the Gemara gives is the obvious one: “If you wish, propose a logical reason, as ordinarily women do not have a beard.” That is, since women can’t grow beards, the rule doesn’t apply to them at all. But the rabbis go on to point out that, in fact, sometimes women do grow facial hair; there is even a baraita stating that “the beard of a woman … is considered like a beard for all matters.” Shouldn’t it follow that, if a woman grows facial hair, she must not destroy it? Once again, it takes some interpretive dexterity to show why women are not included in this prohibition, this time focusing on the singular Hebrew verb in the commandment. Whenever such arguments are employed, I can’t help feeling that the rabbis are arguing ex post facto—that is, they are finding textual reasons to defend what they already believe in as tradition, or simply as common sense.