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Eruvin 48


QUESTION: Rebbi Chiya reported (47b) that a Tana said that if there is a reservoir between two cities, it is forbidden for each city to draw water from the reservoir on Yom Tov (and certainly on Shabbos, when there is the additional problem of carrying in Reshus ha'Rabim). The reason is because at the onset of Yom Tov, the water near one city was Koneh Shevisah with that city, and is limited to that city's Techum. When the residents of the second city draw water from the reservoir on Yom Tov, they might be drawing water that came from the side of the other city and is now beyond its permitted Techum. However, if a Mechitzah of iron was placed in the reservoir, separating the water of each city, then each city may draw water from the reservoir on Yom Tov.

The Gemara concludes that an iron Mechitzah is not necessary. Rather, the Chachamim were lenient with regard to Mechitzos in water and any Mechitzah which is at least ten Tefachim high serves to create a division between the water of each city. The Gemara mentions that this ruling is in accordance with the opinion of Rebbi Yochanan ben Nuri, who maintains that objects of Hefker (such as water) are Koneh Shevisah.

The RIF and ROSH, as well as the SHULCHAN ARUCH (OC 402), rule in accordance with this Gemara, that a reservoir between two cities needs a Mechitzah in order for the cities to be permitted to draw water from it on Yom Tov.

Why do they rule like our Gemara, if this Halachah was only said according to Rebbi Yochanan ben Nuri? The Gemara earlier (46a) said explicitly that the Halachah does not follow the opnion of Rebbi Yochanan ben Nuri with regard to objects of Hefker. Objects that are Hefker are *not* Koneh Shevisah! (Indeed, a number of Rishonim rule that no Mechitzah is necessary because the water in the reservoir is not Koneh Shevisah, like the Rabanan of Rebbi Yochanan ben Nuri -- see, for example, RITVA. The RAMBAM, too, leaves out this Halachah entirely.)


(a)The MAGEN AVRAHAM (ibid.) suggests that although the Gemara says that this Halachah is like Rebbi Yochanan ben Nuri, that was only an initial assumption (which was suggested of necessity to explain why Rebbi Yosi b'Rebbi Chanina laughed at the Halachah that Rebbi Chiya taught). In truth, though, the Rabanan also agree with this Halachah. Just as the Rabanan agree that rain water that fell near a city is Koneh the Shevisah of that city because the people intend to use that water, here, too, the water in the reservoir is Koneh the Shevisah of the city which is adjacent to it.

(TOSFOS (47b, DH Cherem), in fact, asks this as a question on the Gemara; why did the Gemara suggest that this Halachah conforms only to the opinion of Rebbi Yochanan ben Nuri? Even the Rabanan should agree in this case, for it is similar to rain water that fell near a city! Tosfos answers that since the water in the reservoir near the city tends to flow away towards the other city, the people of the first city do not have their minds on that water, and it therefore becomes like any other object of Hefker which is not Koneh Shevisah. The Magen Avraham's answer is not simple, though, because the Gemara shows no indication of a retraction from its original statement that the Halachah of the iron wall only applies according to the opinion of Rebbi Yochanan ben Nuri.)

(b) The VILNA GA'ON suggests that the Rif and Rosh did not have the three lines in the Gemara stating that this Halachah is specific to the opinion of Rebbi Yochanan ben Nuri. Once this text is omitted, the Gemara never asserted that the Halachah was specific to the ruling of Rebbi Yochanan ben Nuri. (This answer is not simple, because we find this text in all of the known editions of the Shas -- even Dikdukei Sofrim.)

The BI'UR HALACHAH concludes that this ruling of the Shulchan Aruch remains difficult to understand.


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