Rabbis speak about “fences.” What are these fences? (Of course, Fences is a play by August Wilson, in which your correspondent’s Uncle Herb Glickman (z”l) is mentioned, but we digress.)
Rabbis specifically speak of “making a fence around the Torah,” “asu seyag laTorah.” It actually appears in the very first paragraph of Pirkei Avot: “Moshe received the Torah from Sinai and transmitted it to Yehoshua, and Yehoshua to the Elders, and the Elders to the Prophets, and the Prophets transmitted it to the Men of the Great Assembly. They said three things: Be deliberate in judgment, raise up many disciples and make a fence around the Torah.”
Building fences is predicated on God instructing our ancestors to safeguard the mandates for the good and against the not-good, such as in Leviticus 18:30 (in the current parashah, Aharey Mot), “You shall keep My charge not to engage in any of the abhorrent practices that were carried on before you…,” the key word being ush’martem, the base of which is shamar, “to guard, keep, observe.” It reminds us of the prayer “Shomer Yisrael, shemor she’erit Yisrael,” “Guardian of Israel, guard the remnant of Israel.”
The idea behind the fences is to instruct folks to follow more stringent rules in order to be absolutely certain to keep the underlying law (or Law). For instance, we are not allowed to spend money on Shabbat. In order to be certain we adhere to that prohibition, we are instructed not to even touch money on Shabbat. (This is the principle of muktseh.)
If there is a pothole on the street, and a public works official sprays the circumference with glow paint, she has created a fence around the pothole, lest we fall in. If the hole is large enough, the official may put up sawhorses or even close that block of the road until the hole is fixed.
That last thought brings us to discussion in which many rabbis have engaged as to the ephemerality of the fences. Witness the prior custom against eating legumes on Pesah (a prohibition not created by rabbis), since rethought by rabbis.
In a sort of reverse fence, Rabbi Gershom ben Judah (c. 960-1040) around 1000 CE instituted prohibitions against polygamy (and divorcing a woman against her will, reading private mail, etc.), even though it was not Biblically prohibited. To justify the ruling, he gave it a sunset time of 1,000 years. The thousand years having expired, do we undo Rabbi Gershom’s reverse fence and go back to polygamy?
And this leads us to rabbis re-evaluating our fences in light of the current times. Of course we must build our fences so that they do not keep us out more than they keep us safe. We trust the rabbis to balance on that fence that both keeps the Law and keeps us secure - ever holier - as well.