Siman - Eruvin Daf 77
- Moving things on a thin wall dividing two chatzeiros
The Gemara brings a machlokes regarding a wall between two chatzeiros that is ten tefachim high but not four tefachim wide. Rav said, אויר שתי רשויות שולטת בהן – the airspace of the two domains, meaning the unmerged chatzeiros, control the top of the wall, לא יזיז בו אפילו מלא נימא – therefore, one may not move anything on it, even as much as the fullness of a hair. The Gemara clarifies that the top is a makom petur and it should be mutar to carry on top of the wall, and even to carry from the top of the wall to each chatzeir, as we find that it is permitted to carry from a makom petur to a reshus hayachid, and to a reshus harabim. However, Rav holds, חכמים עשו חיזוק לדבריהם יותר משל תורה - the Rabbanon strengthened their own enactments, meaning they were more machmir with איסורי דרבנן out of concern that people will violate them in order to move things between two chatzeiros, than they were that people will violate an איסור דאורייתא in a similar situation. Rebbe Yochanan disagrees with Rav and holds that people can even carry food from their chatzeir to the top of the wall since it is a makom petur.
- A wall separating two chatzeiros on different levels
Rabbah said in the name of Rav Huna who said in the name of Rav Nachman, כותל שבין שתי חצרות – a wall which is between two chatzeiros, צידו אחד גבוה עשרה טפחים – if one of its sides is ten tefachim high, וצידו אחד שוה לארץ – and one of its sides is level with the ground of the other chatzeir, which Rashi explains to mean it does not reach a full ten tefachim, נותנין אותו לזה ששוה לארץ – we give the use of the top of the wall to this chatzeir which its ground is level with the wall, משום דהוה לזה תשמישו בנחת – because for the residents of the upper chatzeir it is easy to use, since the top of the wall is within ten tefachim of the chatzeir’s floor, ולזה תשמישו בקשה – and for the residents of the lower chatzeir its use is with difficulty. And in every case where for one chatzeirs use is with ease and the others use is with difficulty, נותנין אותו לזה שתשמישו בנחת – we give use of it to this chatzeir for which the use is with ease.
- Which ladders reduce the height of a wall
The Gemara introduces a ruling regarding reducing the height of the wall below ten tefachim so that its top can be considered a portal. סולם המצרי אינו ממעט והצורי ממעט – An Egyptian ladder does not reduce the height of the wall when leaned against it but a Tyrian ladder does. An Egyptian ladder has less than four rungs, and a Tyrian ladder has four. Rav Acha the son of Rava asked Rav Ashi why the Egyptian ladder does not work to reduce the height of the wall and Rav Ashi explained, משום דהוה ליה דבר שניטל בשבת – because it is something that may be moved on Shabbos, וכל דבר שניטל בשבת אינו ממעט – and anything that may be moved on Shabbos does not reduce the height of the wall. Since the צורי ladder is heavy, it will presumably not be moved on Shabbos, which makes it as if it is permanent.
