what he gains in distance through his eiruv on one side of the city he loses on the other side.

GEMARA: It might enter your mind to say that when the mishna states that one was standing to the east, it means that he was standing to the east of his house and that he had instructed his son to establish an eiruv to the west of his house. Similarly, when it states that he was standing to the west, it means that he was positioned to the west of his house and that he had instructed his son to establish an eiruv to the east of his house. In such a case, the person’s house is located between him and his eiruv.

If so, the question arises: Granted, the mishna’s case where there is a distance of two thousand cubits from his current location to his house, and the distance to his eiruv is greater than this, you can find, as it is possible that he can reach his house without traveling two thousand cubits and he cannot reach his eiruv. But where do you find a case where there is a distance of two thousand cubits between him and his eiruv, and the distance to his house is greater than this? The person’s house is located between him and his eiruv.

Rabbi Yitzḥak said: Do you think that to the east means that he was standing to the east of his house, and to the west means that he was standing to the west of his house? No, to the east means to the east of his son, who is depositing his eiruv for him, and to the west means to the west of his son.

Rava bar Rav Sheila said: Even if you say that to the east means to the east of his house and to the west means to the west of his house, the mishna can be understood as referring to a case where his house stood along a diagonal line in relation to the person and his eiruv. In that case, although he is to the west of his house and the eiruv is located to its east, he can still be closer to his eiruv than he is to his house.

We learned in the mishna: One who places his eiruv within the outskirts of the city has not accomplished anything. However, if he places it outside the city limits, it is effective. The Gemara expresses surprise: Can it enter your mind that the mishna is dealing with a case where one placed his eiruv outside the Shabbat limit? If the eiruv is outside the Shabbat limit as measured from his physical location at the onset of Shabbat, he cannot access it on Shabbat; it is therefore ineffective in establishing his Shabbat residence. Rather, correct it and say as follows: If one placed his eiruv outside the city’s outskirts, i.e., beyond the area of slightly more than seventy cubits surrounding the city, the eiruv is effective in establishing his Shabbat residence at that location.

We learned in the next clause of the mishna concerning one who places his eiruv even one cubit beyond the city’s boundary: That which he gains on one side of the city he loses on the other. The Gemara expresses surprise: Does that mean that only that which he gains on one side he loses on the other, and no more? Wasn’t it taught in a baraita: With regard to one who places his eiruv within the outskirts of the city, he has not done anything; if, however, he placed it outside the outskirts of the city, even one cubit outside, he gains that cubit and loses the entire city because the measure of the city is included in the measure of his Shabbat limit? If one’s Shabbat residence had been in the city, the two thousand cubits of his Shabbat limit would have been measured from the edge of the city’s outskirts; now that he has established his Shabbat residence outside the city, the city itself is included in the two thousand cubits, and he may lose far more on that side than he will gain on the other side.

The Gemara answers: This is not difficult. Here the baraita is referring to a case where his measure of two thousand cubits terminated in the middle of the city; whereas there the mishna is referring to a case where his measure terminated at the far end of the city.

And this is in accordance with the opinion stated by Rabbi Idi, as Rabbi Idi said that Rabbi Yehoshua ben Levi said: If one was measuring the two thousand cubits of his Shabbat limit from the location of his Shabbat residence outside the city, and his measure terminated in the middle of the city, he has only half the city, i.e., he may walk only to the end of his two thousand cubits. If, however, his measure terminated at the far end of the city, the entire city is regarded as four cubits, and he completes the rest of the Shabbat limit on the other side of the city.

Rabbi Idi said: These are nothing more than words of prophecy, i.e., I do not see the logic behind this statement. What difference is it to me if the measure terminated in the middle of the city, or if it terminated at the far end of the city?

Rava said: They are not words of prophecy, as both cases were taught in the following mishna: The residents of a large city may walk through an entire small city that is fully included within its Shabbat limit; the small city is considered as though it were four cubits, and the rest of the Shabbat limit is measured from the other side of the city.