On today’s daf, the rabbis are trying to figure out the specific circumstances surrounding a rule we encountered in a mishnah on yesterday’s page. The rule seems to be pretty straightforward:
If one placed his eruv in a tree above ten handbreadths from the ground, his eruv is not a valid eruv; if it is below ten handbreadths, his eruv is a valid eruv.
We’re discussing here the eruv techumin, the boundary extender that enables a person to walk farther than would normally be permitted on Shabbat. As we’ve seen already, this allowance is effectuated by placing a quantity of food at some distance from one’s home, thus extending the radius one is allowed to travel. The mishnah’s rule seems pretty simple — if you’re placing such an eruv in a tree, it must be at a height below ten handbreadths. Anything above that height, and the eruv is invalid.
For reasons that are hard to summarize (but you should definitely read yourself!), the rabbis determine that the case the mishnah is referring to is one in which someone is trying to place an eruv in a tree that sits in a public domain outside the city limits. The tree has a horizontal branch that extends from the trunk a distance of more than four amot and then turns vertical to a height of more than ten handbreadths. If the eruv is placed on the extended branch below 10 handbreadths, it is a valid eruv. Above that height, it’s not valid.
Oh, and one more thing: This whole situation applies only when the person is attempting to make use of the eruv on a Friday bein hash’mashot — literally “between the suns,” the rabbinic expression for twilight, the period between the setting of the sun and the onset of night.
Why only then? The rabbis are concerned about the person’s ability to retrieve the eruv food on Shabbat, and we know that moving an item between public and private domains constitutes hotza’a and is forbidden. The rabbis considered the area of a tree above ten handbreadths in height to be a private domain, and in this case the area beneath the tree is public, so retrieving the eruv food on Shabbat would require transferring the food from a private to a public area.
But if the food is placed on the extended branch beneath a height of ten handbreadths, both it and the person retrieving it are in the public domain, so there’s no transference problem. But there is a different problem, since according to rabbinic law it’s forbidden to remove an item from a tree on Shabbat.
Here’s where the timing issue becomes important. Twilight on a Friday is neither fully a weekday nor yet fully Shabbat, and according to Rabbi Yehuda Hanasi, Shabbat rules that are purely rabbinic in origin do not apply during this time. Hence, the ruling described in the mishnah must apply only during twilight.
Confused? You should be. This is the sort of head-spinning technical discussion Eruvin is renowned (or feared) for.
But the amazing thing is, the logic doesn’t end here. From this highly unusual case of a person who wants to establish an eruv in a tree, in a public domain, outside of a city, with an elongated branch of more than four amot, at less than ten handbreadths high, during the twilight hour, the rabbis derive a much broader principle: rabbinic Shabbat laws do not apply during the final period before nightfall on Friday. Not just in matters relating to an eruv, but always. Which for anyone who has found themselves rushing on a Friday with last minute Shabbat preparations, turns out to be mighty useful.