Eruvin 6A

מצידו ⁠— בעשר, מראשו ⁠— בארבעה.

if it was breached from its side, the side wall of the alleyway, carrying within the alleyway is prohibited if the breach is 10 cubits wide. But if it was breached from its front, the wall that faces the public domain, carrying within the alleyway is prohibited even if the breach is only 4 handbreadths wide.

מאי שנא מצידו בעשר ⁠— דאמר פתחא הוא, מראשו נמי נימא פתחא הוא!

The Talmud poses a question: What is the difference such that carrying is prohibited due to a breach from the side only if the breach is 10 cubits? This is because you say that up to 10 cubits it is deemed an entrance. If the breach is in the front, let us also say it is an entrance, and carrying should be permitted if the breach is less than 10 cubits.

אמר רב הונא בריה דרב יהושע: כגון שנפרץ בקרן זוית, דפתחא בקרן זוית לא עבדי אינשי.

Rav Huna, son of Rav Yehoshua, said: We are dealing with a case where the breach is in a corner. Since people do not make an entrance in a corner, a breach of this kind cannot be viewed as an entrance, and if the breach is larger than 4 handbreadths it must be sealed.

ורב הונא אמר: אחד זה ואחד זה בארבעה. וכן אמר ליה רב הונא לרב חנן בר רבא: לא תפלוג עלאי דרב איקלע לדמחריא ועבד עובדא כוותי. אמר ליה: רב בקעה מצא וגדר בה גדר.

Rav Huna disagreed with Rav Ḥanin bar Rava and said: There is no distinction between the side and the front, for in both this case and that, a breach of up to 4 handbreadths is allowed. And so Rav Huna said to Rav Ḥanan bar Rava: Do not dispute me, as Rav himself arrived at a place called Damḥarya and performed an action, i.e., issued a practical ruling, in accordance with my opinion. Rav Ḥanan bar Rava said in response to him: No proof can be brought from that incident, for in that case Rav found an unguarded valley and fenced it in, i.e., Rav saw the need to add a safeguard and was therefore stringent in this case. His ruling, however, was not generally applied.