Siman - Eruvin Daf 25

• Erecting a new partition within the walls to make it a new enclosure

קרפף יותר מבית סאתים שלא הוקף לדירה – A karpaf of more than two beis se’ah which was not enclosed for residential purposes, הרחיק מן הכותל ארבעה ועשה מחיצה – if he moved four tefachim from the old wall and erected a new partition, הועיל – it is effective in being considered a new enclosure of the karpaf, and thereby makes it a קרפף שהוקף לדירה and therefore carrying is permitted. פחות משלשה לא הועיל – If he erected a new partition that was less than three tefachim from the old wall, it is not effective. Since the distance between the partition and the old wall is insignificant, the partition is not recognized as a new enclosure. Rashi explains, דהוי מחיצה על גבי מחיצה – it is comparable to a mechitzah constructed over a pre-existing mechitzah.

It is a machlokes if the distance from the old wall to the new wall was from three to four tefachim. Rabbah said it is effective for re-enclosing the karpaf, because the space between the walls is beyond the distance of lavud, whereas Rava said it is not effective since the area between the walls is not an area of four tefachim it is not considered significant to deem it a new enclosure.

• Putting mud on the inside of the walls to reduce the size of karpaf

The Gemara discusses a method for reducing the area of a karpaf enclosed for non-residential purposes, to two beis se’ah or less.  טח בו טיט – If one applied mud to the inside of the karpaf’s walls, if the mud can stand on its own, it is an effective form of reduction and therefore carrying is permitted. If the mud cannot stand on its own, Rabbah says, הוי מיעוט – it is an effective form of reduction, השתא מיהא קאי – because now, at least, the mud is standing, whereas Rava says, לא הוי מיעוט – it is not an effective form of reduction, כיון דלא יכול למיקם בפני עצמו לא כלום הוא – since the mud cannot stand on its own, it is insignificant, and it does not reduce the size of the karpaf.

• If the outer wall of a mansion collapsed next to an orchard

ההוא בוסתנא דהוה סמיך לגודא דאפדנא - There was an orchard that was adjacent to the wall of a mansion, and the outer wall of the mansion, which served as a wall of the orchard, collapsed. Even though this wall was the only one to enclose the orchard for residential use, and with its collapse one would have thought that carrying would now become prohibited since the orchard was greater than two beis se’ah, Rav Bivi thought to say, ליסמוך אגודא גוויאתא – that they may rely on the inner wall of the house. Since the inner wall was constructed to enclose the house for dwelling purposes, it should enclose the orchard for the same purpose.

Rav Pappi said to Rav Bivi that his reasoning was incorrect. Since the inner walls were made for the inside of the house and were not constructed to enclose the orchard for residential purposes, carrying in the orchard remains prohibited.