TB Eruvin 23 What the rabbis give, the rabbis take away.

Chapter 2 of TB Eruvin began discussing the scenario of a well in the public domain. A well of foursquare handbreadths in area with a surrounding wall of 10 handbreadths high is a private domain. By drawing water from this private domain we would transfer it immediately to a public domain which is obviously forbidden. In between all the Aggadah, the Gemara does discuss the amazing leniency of virtual walls created by the four brackets and upright boards (פַּסֵּי בֵירָאוֹת) to turn the area around a well or a cistern that collects water into a private domain in order to draw water.

Almost immediately though, the Gemara begins to limit this leniency of these virtual walls. First of all, they only benefit those traveling to Jerusalem for the three pilgrimage holidays or for other similar mitzvot. Rashi provides the only other example of going from one yeshiva to another in order to study Torah. Secondly, the water drawn can be used only for the person’s animals and not to quench his own thirst. If the person wants water for himself, he must scale down the walls of the well. I imagine he can brace himself against the back wall of the well with his back as he goes down. Although I can’t think of too many people who would be willing to do that for a drink of water. However if the well is too wide for that possibility, the person may also drink from the well’s water by drawing it up.

Today’s daf Eruvin 23 discusses further limitations on the bottom of the previous page TB Eruvin 22b. “MISHNA: In the case of a public cistern containing collected water, as well as a public well containing spring water, and even a private well, one may arrange upright boards around them in order to allow one to carry in the enclosed area, as delineated above.

 But in the case of a private cistern, there are two deficiencies: It belongs to an individual, and it does not contain spring water. Consequently, it is impossible to permit drawing from it on Shabbat by means of boards set up in the corners; rather, one must construct for it a proper partition ten handbreadths high; this is the statement of Rabbi Akiva.

Rabbi Yehuda ben Bava says: One may arrange upright boards only for a public well. But for the others, that is, a public cistern or a private well, one must set up a belt, i.e., a partition consisting of ropes, ten handbreadths high. Such an arrangement creates a proper partition based on the principle of lavud, namely, that solid surfaces with gaps between them smaller than three handbreadths are considered joined.” (Sefaria.org translation)

A well is better than a cistern because the well will always have water from its underground source. A cistern relies on collected rainwater and the water can dry up during the hot summer months. Public is better than private because in the public domain there will be lots of people to remind you of the correct halakha concerning the well or the public cistern.

As you can read the Tanna kamma holds the most lenient position that these virtual walls work in all cases and Rabbi Yehuda ben Bava holds the most stringent position that these virtual walls only work for wells. Rabbi Akiva’s position is somewhere in the middle saying that private cisterns need real walls and not these virtual ones. Today’s daf informs us that the halakha is according to Rabbi Yehuda ben Bava.

“GEMARA: Rav Yosef said that Rav Yehuda said that Shmuel said: The halakha is in accordance with the opinion of Rabbi Yehuda ben Bava. And Rav Yosef also said that Rav Yehuda said that Shmuel said: Upright boards surrounding a well were permitted only in the case of a well containing potable, running spring water.

The Gemara comments: And it was necessary to cite both of these statements, even though their content appears to be the same. As had he taught us only that the halakha is in accordance with the opinion of Rabbi Yehuda ben Bava that upright boards may only be set arranged for a well, I would have said that with regard to water belonging to the public, upright boards are permitted not only in the case of spring water, but even in the case of water collected in a cistern.

And that which was taught: One may only arrange boards for a public well, that was to exclude the opinion of Rabbi Akiva that upright boards may be arranged even for a private well, but not to allow us to infer that boards may not be arranged for a public cistern filled with collected water. Therefore, Shmuel teaches us that boards surrounding a well were permitted only in the case of a well of spring water.

And in the opposite direction, had he taught us that upright boards may only be arranged for a well containing potable, running spring water, I would have said that there is no difference whether it is a public well and there is no difference whether it is a private well. Shmuel therefore teaches us that the halakha is in accordance with the opinion of Rabbi Yehuda ben Bava, who says that upright boards may be arranged only for a public well, but not for one that belongs to an individual.” (Sefaria.org translation)

So as you can see, what the rabbis give, the rabbis take away.