Tosfos says that chazal made a takana that an eruv t'chumim will not take effect if it is outside the person's default t'chum during bein hash'mashos, because the person is outside the t'chum that he is trying to establish, and will end up stuck in his 4 amos.
If I recall correctly, we will be seeing some cases later in which city A is in city B's t'chum but not vice versa. Would it be possible for the person to be within the t'chum that he is trying to establish, but to have the food outside his default t'chum? Would chazal still make their takana and invalidate his attempted eruv?
Marc Diamond, Providence, RI
If the food is outside of his default Techum, even though it is in the Techum he is trying to establish the Eruv will not work (since the person making the Eruv will be more than 2000 Amos away from his Shevisah). The Rabanan will therefore make the same Takanah and invalidate his Eruv.
Tosfos says that chazal made a takana that an eruv t'chumim will not take effect if it is outside the person's default t'chum during bein hash'mashos, because the person is outside the t'chum that he is trying to establish, and will end up stuck in his 4 amos. We see a case later we in which city A is in city B's t'chum but not vice versa. Would it be possible for the person to be within the t'chum that he is trying to establish, but to have the food outside his default t'chum? Would chazal still make their takana and invalidate his attempted eruv?
The case I am refering to is on daf 61a, Hamsan & Geder. B'nei Geder can go to Hamsan on shabbos, but not vice versa. According to the approaches of Rav Safra and Rav Dimi bar Hin'na (ir k'keshes or ir g'dola v'ir k'tana), if Reuven lives in Geder, begins shabbos in Geder, but leaves his eruv in Hamsan, he is now in a situation similar to the eruv that got away on daf 35a. The eruv is within his default t'chum, but he is not within his attempted t'chum. Would tosfos hold that he only has 4 amos? Is this case parallel to the case of someone who lives near the middle of a big city and puts his eruv outside the city, more than 2000 amos from his home, discussed in mishna b'rura 108:3 and biur halacha there? In that case there are three possibilities: the eruv doesn't work ("a very big chiddush"), the eruv works and he can walk to it but not back to his house, or the eruv works and he can even walk back to his house. What about a fourth choice: the eruv works, and he is stuck in his 4 amos?
My question is in the reverse case: Shimon lives in Hamsan, begins shabbos in Hamsan, but leaves his eruv in Geder. During bein hashmashos the eruv is outside his default t'chum, but he is within the t'chum of his attempted eruv. What would the tosfos on 35a hold regarding this case?
I'm afraid I am still not clear what you mean. So let me just explain the Tosfos on 35a and then see whether it is connected with the Sugya in 61a.
Incidentally, Tosfos is merely explaining the Mishnah, so it is really the Mishnah's opinion that we are talking about, not Tosfos'.
What Tosfos says is that if someone's Eiruv rolls five Amos from where he places it (i.e. to 2005 Amos from his home), it is ineffective (meaning that it would not take effect at the spot where he placed it), even though, during Bein-ha'Shemashos, he would have been permitted to retrieve it and put it back there. And the reason for this is because if he were to be Koneh Shevisah there, where the Eiruv is actually located now, he would be forbidden to walk more than four Amos.
On Daf 61a. the Gemara forbids the residents of Chamsan to traverse the whole of Geder because (according to Rav Dimi bar Chin'na) the two thousand Amos from where the Eiruv was placed terminated in the middle of Geder (as the Gemara explained earlier). Whereas the residents of Geder were permitted to traverse the whole of Chamsan plus, because (counting the town as four Amos), they were permitted to add on however many Amos were still missing to make up two thousand Amos from where the Eiruv was placed. Either way, the Eiruv was placed two thousand Amos from the edge of the respective towns, not two thousand and five (which would have made it similar to the case of Nisgalgel).
Consequently, there does not seem to be any connection between the two cases.
be'Virchas Kol Tuv