On today’s daf, we continue to discuss the laws of transporting objects on Shabbat within an alleyway that is open on one side to a public space. In the Talmud, an alleyway like this is referred to as a mavoi (pronounced mah-VOY). Tractate Eruvin is full of spaces like this that are neither fully public nor fully private. The rabbis were concerned that a mavoi, while closed on three sides and technically a private domain, could be easily confused with a public domain. So they instituted an adjustment to transform the mavoi into a space within which you may carry on Shabbat.
There are different mechanisms to effect this transformation, one of which is a horizontal beam, known as a korah (KOE-rach). When attached to the opening of a mavoi, the korah can be considered a significant enough marker to allow carrying within it on Shabbat.
We’ve already seen the rabbis discussing how high the korah must be to permit carrying within a mavoi. But on today’s daf, the rabbis entertain a more fundamental disagreement about the nature of the korah.
This Master, Rav Yosef, holds that a cross beam functions in an alleyway as a conspicuous marker that demarcates the alleyway from the public domain, and consequently a mere handbreadth is sufficient, as even a handbreadth is sufficiently conspicuous. And this Master, Abaye, holds that a cross beam serves as a partition, and a partition is not effective for an area of less than four handbreadths.
The rabbis are here debating how wide a korah must be in order to serve its function. According to Abaye, the beam serves as a structural element that symbolically creates a fourth wall in the mavoi, such that the alleyway is now effectively surrounded on all sides. And so the korah must be at least four handbreadths wide. But according to Rav Yosef, the concern is not the space but the people carrying within it. The korah serves as a reminder to people who might forget and carry outside the mavoi. As long as the korah is wide enough to achieve that — one handbreadth, per Rav Yosef — it’s sufficient.
It is possible that Abaye and Rav Yosef are not only arguing about the function of the beam, but also about the underlying concern that necessitated the beam in the first place. According to Rav Yosef, there is no problem with carrying in a mavoi as long as we take steps to ensure people don’t accidentally carry outside of it. But according to Rav Yosef, the problem is more fundamental. It’s actually not kosher to carry in the unadjusted mavoi at all. Doing so makes it appear that you are carrying in a semi-public area. So a more substantial fix is necessary.
As we progress through Eruvin, we will continue to see various approaches to demarcating space for the purpose of carrying on Shabbat. From a flimsy wire to a beam to a solid brick wall, each has its own purpose and role.