Talmud - Eruvin 15a עירובין ט״ו א׳

It was stated that the amora’im disagreed about a side post that stands by itself, i.e., a side post at the entrance to an alleyway that was not put there for the express purpose of permitting one to carry on Shabbat. Abaye said: It is a valid side post. Rava said: It is not a valid side post.

The Gemara first narrows the scope of the dispute: In a place where the inhabitants of the alleyway did not rely on it from yesterday, e.g., the alleyway had another side post that fell down on Shabbat, all agree that it is not a valid side post. Where they disagree is in a case where they relied on it from yesterday. Abaye said: It is a valid side post, as they relied on it from yesterday. Rava said: It is not a valid side post; since it was not originally erected for this purpose, it is not considered a valid side post.

The Gemara comments: It might enter your mind to say that just as they disagree with regard to a side post, they also disagree with regard to whether a partition that was not erected to serve that function is considered a valid partition.

Come and hear a proof based upon what we learned in the following mishna: With regard to one who makes his sukka among the trees, and the trees serve as its walls, it is a valid sukka. This proves that the trees function as partitions even though they were not erected for this purpose. The Gemara responds: With what are we dealing here, in this mishna? To a case where he planted the trees from the outset for this purpose. The Gemara asks: If so, it is obvious that the trees constitute valid walls. The Gemara answers: Lest you say the Sages should issue a decree to prohibit using a sukka with trees as its walls, due to a concern that perhaps one will come to use the tree on the Festival and detach a branch or leaf in the process, the mishna therefore teaches us that no such decree was made and the sukka is permitted.

The Gemara tries to present another proof. Come and hear a proof from a baraita: If there was a tree there, or a fence, or a barrier of reeds that are interconnected and form a hedge, it is judged to be a valid double post, i.e., it qualifies as a partition suitable to enclose a public well, as will be explained below. This indicates that a partition not constructed to serve as a partition is nonetheless valid.

The Gemara rejects this proof: Here, too, with what are we dealing? With a case where one constructed them from the outset for this purpose. The Gemara asks: If so, what does it teach us; is it not obvious that it is a valid double post? The Gemara answers: It teaches us that a barrier of reeds is a valid partition if the distance between one reed and the next is less than three handbreadths, as Abaye raised this dilemma to Rabba, and the baraita teaches that it is valid.

The Gemara suggests another proof. Come and hear a proof from the following mishna: With regard to a tree whose branches hang over from a height of greater than ten handbreadths and reach almost to the ground, if the ends of its branches are not higher than three handbreadths from the ground, one may carry under it; the branches constitute partitions all around, and it is therefore permissible to carry in the enclosed area. The Gemara responds: Here, too, with what are we dealing? With a case where he planted the tree from the outset for this purpose.

The Gemara asks: If so, it should be permitted to carry in all of it no matter how large the area. Why, then, did Rav Huna, the son of Rav Yehoshua, say: One may only carry under the tree if its branches enclose an area no larger than two beit se’a, i.e., five thousand square cubits? If the area is larger, it is not considered a courtyard, and carrying there is prohibited. This indicates that the branches are not considered full-fledged partitions.

The Gemara answers: The reason that carrying is permitted only if the enclosed area is less than this size is because it is a dwelling whose use is for the open air beyond it, i.e., it is used by guards who are watching the fields beyond it, rather than as an independent dwelling place, and the halakha with regard to any dwelling whose use is for the open air beyond it is that one may carry in it only if its area is no larger than two beit se’a.

The Gemara suggests another proof. Come and hear that which was taught in the following baraita: With regard to one who established his Shabbat abode on a mound that was ten handbreadths high and its area was anywhere from four cubits to the two beit se’a; and similarly, one who established his Shabbat abode in a natural cavity of a rock that is ten handbreadths deep and its area was anywhere from four cubits to two beit se’a; and similarly, one who established his Shabbat abode in a field of reaped grain, and rows of stalks ten handbreadths high that have not been reaped surround it, serving as a partition enclosing the reaped area, he may walk in the entire enclosed area, and outside it an additional two thousand cubits. This indicates that a partition not specifically constructed to serve as a partition is nonetheless valid.

And if you say that here, too, it is a case where he made it from the outset for this purpose, there is a difficulty. Granted, in the case of the grain, this answer is all right; but with regard to a mound and a cavity, what can be said? They were there from time immemorial and were not constructed to serve as partitions.

Rather, the Gemara rejects its previous argument and explains: With regard to partitions, all agree that a partition that stands by itself is a partition, despite the fact that it was not erected for that purpose. Where they disagree is with regard to a side post. Abaye follows his usual line of reasoning, as he said that a side post serves as a partition, and a partition that stands by itself is a valid partition. And Rava follows his usual line of reasoning, as he said that a side post serves as a conspicuous marker. Therefore, if it was made with a person’s hands for that purpose, it is considered a conspicuous marker; and if not, it is not considered a conspicuous marker.

The Gemara now attempts to prove which side is correct according to this version of the dispute. Come and hear a proof from the Tosefta: With regard to stones of a wall that protrude from the wall and are separated from each other by less than three handbreadths, there is no need for another side post in order to permit carrying in the alleyway; the protruding stones join together to form a side post. However, if they are separated by three handbreadths, there is a need for another side post. This indicates that a side post is valid even if it was not erected for that purpose.

The Gemara rejects this proof: Here, too, we are dealing with a case where one built them from the outset for this purpose. The Gemara comments: If so, it is obvious that the side post is valid. The Gemara explains: Lest you say that it was only in order to connect the building to another building that he built the wall with protruding stones, it teaches us that it is a valid side post. We are not concerned that onlookers might assume that the wall was not originally built as a side post.

The Gemara suggests another proof: Come and hear the following Tosefta taught by Rabbi Ḥiyya: A wall, one side of which is more recessed than the other, whether the indentation is visible from the outside and the wall looks even from the inside, or it is visible from the inside and the wall looks even from the outside, it is considered a side post. This indicates that a side post is valid even if it was not erected for that purpose.

The Gemara answers: Here, too, it is a case where one fashioned it from the outset for this purpose, to serve as a side post. The Gemara asks: If so, what does it teach us? The Gemara answers: This teaches us that a side post that is visible from the outside and looks even with the wall from the inside is considered a side post, although this view is not universally accepted.

The Gemara suggests another proof: Come and hear the following story: Rav was sitting in a certain alleyway, and Rav Huna was sitting before him. He said to his attendant: Go, bring me a small pitcher of water. By the time he came back with the water, the side post at the entrance to the alleyway had fallen. Rav signaled to him with his hand that he should stop, and the attendant stood in his place. Rav Huna said to Rav: Doesn’t the Master hold that it is permissible to rely on the palm tree located at the entrance to this alleyway as a side post? Rav said: This scholar, Rav Huna, is comparable to one who does not know the teachings of the Sages. Did we rely on the palm tree from yesterday? Since we did not, carrying in the alleyway is not permitted.

Based on Rav’s response, the Gemara argues as follows: The reason that the palm tree could not serve as a side post is because we did not rely on the palm tree from yesterday. This indicates that had we relied on it, it would be a valid side post, thus proving that a side post that was not erected for that purpose is nonetheless valid, in accordance with the opinion of Abaye.

The Gemara suggests: Shall we say that Abaye and Rava disagree only in a case where they did not rely on it before Shabbat, but in a case where they did rely on it, all agree it is a valid side post? The Gemara answers: This should not enter your mind, as there was a certain balcony [barka] that was in the house of Bar Ḥavu that Abaye and Rava disagreed about their entire lives. The residents of the alleyway began relying on a pillar upon which the balcony rested as their side post. Since Abaye and Rava disagreed about this case, it is clear that their disagreement applies even when the residents had relied on the item as a side post from before Shabbat.

MISHNA: One may construct side posts from anything, even a living creature, provided that it was properly attached to the entrance of the alleyway, and Rabbi Meir prohibits using a living creature as a side post. The mishna continues with a similar dispute: Even a living creature imparts ritual impurity if it used as the covering of a grave.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Eruvin 15a examines Abaye and Rava's dispute over whether a pre-existing side post or unbuilt partition validly permits carrying, using the sukka-among-trees case as proof.