Eruvin 9A

משוכה או תלויה, פחות משלשה ⁠— אין צריך להביא קורה אחרת. שלשה ⁠— צריך להביא קורה אחרת. רבן שמעון בן גמליאל אומר: פחות מארבעה ⁠— אין צריך להביא קורה אחרת, ארבעה ⁠— צריך להביא קורה אחרת.

drawn away from the alleyway walls or suspended in the air, the following distinction applies: If the cross beam is less than 3 handbreadths from the walls, one is not required to bring a different cross beam, for it is considered attached to the walls based on the principle of lavud, which views two solid surfaces as connected if the gap between them is less than 3 handbreadths wide. However, if the distance is 3 or more handbreadths from the walls, he is required to bring a different cross beam in order to permit carrying in the alleyway. Rabban Shimon ben Gamliel, who holds that the principle of lavud applies to a gap of up to 4 handbreadths wide, says: If the cross beam is less than 4 handbreadths from the wall, one is not required to bring a different cross beam; but if the distance is 4 handbreadths from the wall, he is required to bring a different cross beam.

מאי לאו ⁠— משוכה מבחוץ, ותלויה מבפנים!

The Talmud wishes to clarify the baraita: What, is it not that when the baraita speaks of a cross beam that is drawn away from the alleyway walls, it is referring to a cross beam that is distanced from the alleyway walls and situated on the outside in the public domain, similar to the case of the cross beam resting on pegs mentioned above? And when it speaks of a cross beam that is suspended, isn’t it referring to a cross beam that is distanced from the alleyway walls and placed on the inside in the alleyway? This interpretation contradicts Rava’s statement above that disqualifies such a cross beam.