גמ׳ למקום שריבה אין למקום שמיעט לא אימא אף למקום שריבה:
GEMARA: The Gemara asks: Does this mean that in a place where he extended the limit, yes, the surveyor’s measurements are accepted, but in a place where he reduced the limit, no, his measurements are not accepted? If his extended measurement is accepted, his shortened measurement should certainly be accepted as well. The Gemara answers: Say that the mishna means that the surveyor’s measurements are accepted even in a place where he extended the limit, without concern that he might have erred (Tosafot), and that the surveyor’s measurements are certainly accepted in places where he reduced the Shabbat limit.
ריבה לאחד ומיעט לאחד כו׳: הא תו למה לי היינו הך הכי קאמר ריבה אחד ומיעט אחד שומעין לזה שריבה
We learned in the mishna: If the surveyor extended the limit for one and reduced it for another, one accepts the extended measurement. The Gemara asks: Why do I need this as well? This clause is the same as that previous clause in the mishna. The Gemara answers that this is what the mishna said: If two surveyors measured the Shabbat limit and one extended the Shabbat limit and one reduced it, one accepts the measurements of the surveyor who extended it.
אמר אביי ובלבד שלא ירבה יותר ממדת העיר באלכסונא:
Abaye said: The measurements of the surveyor who extended the limit are accepted only as long as he does not extend the limit more than the difference between the measure of the Shabbat limit of the city calculated as a diagonal line from the corner of the city and as calculated as a straight line from the side of the city. If, however, the difference in measurements exceeds that amount, the Shabbat limit must be measured again.
שלא אמרו חכמים את הדבר להחמיר אלא להקל: והתניא לא אמרו חכמים את הדבר להקל אלא להחמיר
We learned in the mishna: As the Sages did not state the matter, the laws of Shabbat limits, to be stringent, but rather to be lenient. The Gemara asks: Wasn’t the opposite taught in a baraita: The Sages did not state the matter, the laws of Shabbat limits, to be lenient but rather to be stringent?
אמר רבינא לא להקל על דברי תורה אלא להחמיר על דברי תורה ותחומין דרבנן:
Ravina said that there is no contradiction between these two statements: The very institution of Shabbat limits was enacted not to be more lenient than Torah law, but rather to be stringent beyond Torah law. Nonetheless, since Shabbat limits are rabbinic law, the Sages permitted certain leniencies with regard to how the Shabbat limits are measured.
מתני׳ עיר של יחיד ונעשית של רבים מערבין את כולה
MISHNA: Although this chapter as a whole deals with halakhot governing the joining of Shabbat boundaries, this mishna returns to the halakhot governing a joining of courtyards. If a private city, which does not have many residents, grows and becomes a heavily populated public city, one may establish a joining of the courtyards for all of it, as long as it does not include a public domain as defined by Torah law.
ושל רבים ונעשית של יחיד אין מערבין את כולה אלא אם כן עשה חוצה לה כעיר חדשה שביהודה שיש בה חמשים דיורין דברי רבי יהודה רבי שמעון אומר שלש חצירות של שני בתים:
And if a public city loses residents over time and becomes a private city, one may not establish an eiruv for all of it unless one maintains an area outside the eiruv that is like the size of the city of Ḥadasha in Judea, which has fifty residents. Carrying within the eiruv is permitted, but it remains prohibited to carry in the area excluded from the eiruv. The reason for this requirement is to ensure that the laws of eiruv will not be forgotten. This is the statement of Rabbi Yehuda. Rabbi Shimon says: The excluded area need not be so large; rather, it is sufficient to exclude three courtyards with two houses each.
גמ׳ היכי דמי עיר של יחיד ונעשית של רבים אמר רב יהודה כגון דאיסקרתא דריש גלותא
GEMARA: The Gemara asks: What are the circumstances of a private city that becomes a public city? Rav Yehuda said: For example, the Exilarch’s village [de’iskarta] was a small village set aside for the Exilarch’s family and attendants; since it was frequented by many people, it turned into a public city.
אמר ליה רב נחמן מאי טעמא אילימא משום דשכיחי גבי הרמנא מדכרי אהדדי כולהו ישראל נמי בצפרא דשבתא שכיחי גבי הדדי אלא אמר רב נחמן כגון דיסקרתא דנתזואי
Rav Naḥman said to him: What is the reason for bringing this example? If you say that because large numbers of people are to be found at the residence of the governor [harmana] in order to request licenses and authorizations, and they remind each other of the reason it is permissible to establish an eiruv there, and consequently they will not arrive at mistaken conclusions with regard to other places, then every city should have the same status, as the entire Jewish people are also found together on Shabbat morning when they come to pray. Rather, Rav Naḥman said: For example, the village of Natzu’i was a private city belonging to a single individual before a large influx of residents turned it into a public city.
תנו רבנן עיר של יחיד ונעשית של רבים ורשות הרבים עוברת בתוכה כיצד מערבין אותה עושה לחי מכאן ולחי מכאן או קורה מכאן וקורה מכאן ונושא ונותן באמצע ואין מערבין אותה לחצאין אלא או כולה או מבוי מבוי בפני עצמו
The Sages taught in a baraita: If a private city becomes public, and a bona fide public domain passes through it, how does one establish an eiruv for it? He places a side post from here, one side of the public domain, and side post from there, the other side; or, he places a cross beam from here, one side of the public domain, and another cross beam from there, the other side. He may then carry items and place them between these symbolic partitions, as the public domain is now considered like one of the courtyards of the city. And one may not establish an eiruv for half the city; rather, one may establish either one eiruv for all of it or separate ones for each alleyway separately without including the other sections of the city.
היתה של רבים והרי היא של רבים
The baraita continues: If it was originally a public city, and it remains a public city,