- Defining the dalet amos for one who does not have a techum
The Gemara clarifies the three opinions in the Mishnah on Daf 45a who hold that a traveler who fell asleep at the onset of Shabbos does not acquire a makom shevisa and is restricted to dalet amos. The Chochomim hold that he can travel four amos in each direction, giving him a square space of 8x8 amos. Rebbe Eliezer holds that he can only travel two amos in each direction, with him in the center of a four amos square. Rebbe Yehudah agrees that he is restricted to a four amos square, but he can choose where he wants his four amos to be and walk up to four amos in one direction. Rava said, מחלוקת להלך אבל לטלטל דברי הכל ארבע אמות אין טפי לא – the machlokes of four amos or eight amos is only in regard to walking, but in regard to carrying in reshus harabim everyone agrees that only four amos are permitted.
- The source for dalet amos
The Gemara seeks the source that a person without a techum is only permitted to move within a four-amos area, and brings a Baraisa which taught that the passuk, שבו איש תחתיו – sit, each man in his place on Shabbos, כתחתיו – like that which is underneath him. How much is that? גופו שלש אמות – His body when lying down extends three amos, ואמה כדי לפשוט ידיו ורגליו – and he gets one amah in order to stretch his arms and legs, according to Rebbe Meir. Rebbe Yehudah says, גופו שלש אמות – his body when lying down extends three amos, ואמה כדי שיטול חפץ מתחת מרגלותיו ומניח תחת מראשותיו – and he receives one additional amah so that he can take an object from under his feet and place it under his head. The difference between these two opinions is that Rebbe Yehuda only allows an area that is exactly four amos, while Rebbe Meir allows an area slightly larger than four amos. Rashi explains that Rebbe Meir’s method results in slightly more than four amos since a person needs a little more than one amah in which to stretch.
- Three chatzeiros where two outer chatzeiros joined in an eruv with the middle one
In the Mishnah on Daf 45b, Rebbe Shimon likened the case of three people, each limited to a four amah area, where the middle person overlapped, to a case of three chatzeiros which open to one another and also open into reshus harabim, and the two outer chatzeiros each joined in a an eruv with the middle chatzeir. The middle chatzeir is permitted to carry into the outer chatzeiros and the outer chatzeiros can carry into the middle chatzeir, but the two outer chatzeiros are prohibited with each other. The Gemara asks why the residents of the outer chatzeiros are prohibited to carry into each other’s chatzeir if they joined with the middle one. They should all become one entity and carrying should permitted for all of them.
Rav Yehuda says that the case is where the middle chatzeir placed eruvin in the outer chatzeiros, therefore there is nothing merging the outer chatzeiros. Rav Sheishess says that it can even be a case where the outer chatzeiros placed eruvin in the middle chatzeir except they placed them in different houses, and therefore they are not considered as merged. The Gemara analyzes these two opinions.