Adam Kirsch in Tablet:
It’s not often that the subject of the weekly Daf Yomireading makes headlines in the blogosphere. But last week, the web—especially its Jewish corners—was buzzing over a bizarre photograph of an Orthodox Jewish man on an airplane, completely wrapped in a plastic bag. Many commenters on the photo assumed this had something to do with sexual purity or avoiding women, but in fact, as knowledgeable readers pointed out, it actually involved another taboo entirely.
The man must have been a Kohen, a member of the priestly class, and Kohanim are prohibited from coming into contact with corpses. Passing over a cemetery—even, in this case, at 30,000 feet—qualifies as such a contact. By wrapping himself in plastic, the man in question must have been guarding himself against that kind of impurity or tumah. Since most Orthodox Jews, even Kohanim, do not regularly fly in plastic, it’s clear that the man in the photo was adopting a minority position about what’s required to avoid contamination. (I’d be glad to hear from knowledgeable commenters about the law on this issue.)
As it turned out, just this question—how a Kohen can travel through a cemetery—was addressed in the Talmud last week, in Eruvin 30b. The issue arose in connection with the tractate’s ongoing discussion of eruvei techumin, the extension of Shabbat boundaries. As I wrote in my last column, the techum or boundary for walking on Shabbat is 2,000 amot, around 2/3 of a mile. But the place from which this circumference is measured can be shifted, by establishing a Shabbat residence at a different location from the one you actually occupy. To do this, you must deposit food at the spot of your Shabbat residence; and the third chapter of Eruvin has been dedicated to the technicalities of this process.