(a)How does the Gemara initially reconcile Rebbi Yossi in our Mishnah (where he places the Eruv on a Chezkas Taharah), with his own opinion in the Mishnah in Mikva'os (of Safek Taval, where he declares him Tamei - even by a Tum'ah de'Rabbanan)?
(b)An alternative answer is that the opinion that he cites in our Mishnah is not his own, but his Rebbe's. Who is his Rebbi and what did he say in the name of five elders?
(c)Rava explains that Rebbi Yossi is strict by Safek Taval, because the person has a Chezkas Tum'ah. Why do we not contend with the Chezkas Taharah of the Mikveh?
(a)Rebbi Yossi rules Lechumra by Safek Taval, even by a Tum'ah de'Rabbanan - because basically, Tum'ah is d'Oraysa, so we decree by Tum'ah de'Rabbanan, in order that people should not come to deal leniently in cases of Tum'ah d'Oraysa; Eruvin, on the other hand - is purely de'Rabbanan, which is why he is lenient.
(b)Rebbi Yossi quoted Avtulmus, who testified in the name of five elders that Safek Eruv is Kasher.
(c)The reason that, according to Rava, Rebbi Yossi contends with the Chezkas Tum'ah of the person, and not with the Chezkas Taharah of the Mikveh - is because the Mikveh has no Chezkas Taharah. Why not? Because it speaks about a Mikveh which was not previously measured (if it had been, Rebbi Yossi would contend with it).
(a)Rava just explained that Rebbi Yossi is strict by Safek Taval, because the person has a Chezkas Tum'ah. But by Eruv there is also a Chazakah that his residence is his house in town, so why is he lenient there?
(a)Indeed, by Eruv there is also a Chazakah that his residence is his house in town, so when there is a Safek, we ought to say that his place of residence is there. However, against that there is also a Chezkas Taharah of the Terumah, in which case his new Eruv should be valid. Consequently, since we now one a clash of Chazakos, we are lenient, since Eruv is de'Rabbanan.
(a)The Beraisa differentiates in Rebbi Yossi between whether 'Safek mi'be'Od Yom Nitma'as, Safek mi'she'Chasheichah Nitma'as', and 'Erav bi'Terumah, Safek Tehorah Safek Temei'ah'. What is the difference between them?
(b)The Beraisa incorporates in the former case: 've'Chen Peyros Safek mi'be'Od Yom Niskanu, Safek mi'she'Chasheichah Niskanu'. Why can this not be referring to Safek Tevel?
(c)What then, is it referring to?
(a)In the case of 'Safek mi'be'Od Yom Nitma'as, Safek mi'she'Chasheichah Nitma'as', Rebbi Yossi establishes the Terumah on a Chezkas Taharah (which it had when it was initially placed) - therefore he declares the Eruv Kasher; whereas by 'Erav bi'Terumah, Safek Tehorah Safek Temei'ah', where there is no Chezkas Taharah, the Eruv will be invalid.
(b)'ve'Chen Peyros Safek mi'be'Od Yom Niskanu, Safek mi'she'Chasheichah Niskanu, Zehu Safek Eruv, ve'Kasher' cannot be referring to Safek Tevel - because then the food would have a Chezkas Tevel, and the Eruv would not be Kasher.
(c)The Beraisa must therefore read, not 'Peyros Safek mi'be'Od Yom Niskanu' etc., but 'Peyros Safek mi'be'Od Yom Nidme'u' which either means that Terumah fell into the Chulin fruit (but we do not know when it fell in), and the Beraisa will follow the opinion of Sumchus, who invalidates an Eruv of Terumah which is placed for a Yisrael; or that Tevel fell into Chulin, in which case, it may be invalid - according to everyone, whoever the Eruv is placed for.
(a)If someone designates for his Eruv, whichever of the two Terumah loaves lying in front of him which is Tahor, why might ...
1. ... Rebbi Meir concede that his Eruv is valid?
2. ... Rebbi Yossi concede that it is not?
(b)The Gemara concludes that the Eruv is invalid according to both Tana'im. Why is that?
(c)Why can a loaf which the owner declared Chulin on Friday and Hekdesh on Shabbos, make a valid Eruv, whereas if he declared it Hekdesh on Friday and Chulin (redeemed) on Shabbos, it cannot - even though both have the same Safek during the Bein Hashemashos period?
(d)What did Rav Nachman mean when he said to Rava 'Lechi Teichol Aleih Kura de'Milcha'?
1. Even Rebbi Meir may concede that if someone designated for his Eruv, whichever of the two Terumah loaves lying in front of him is Tahor, his Eruv is Kasher - since unlike our Mishnah (where the loaf is Safek Tamei, and there is no case of Vaday Tahor), there is one loaf which is definitely Tahor, so we will place it a Chezkas Taharah.
2. And Rebbi Yossi may well concede that, in this case, we will not validate the Eruv - because in our Mishnah, if the loaf is Tahor, he can identify it (in which case, the Safek cannot detract from the Chezkas Taharah), whereas in our case, he cannot identify the Tahor loaf, and it will therefore remain Safek Tamei.
(b)The Gemara concludes that the Eruv is invalid according to both Tana'im - because the Eruv must be fit to eat by day (which the loaf in the Mishnah was), whereas here, the Tamei loaf was definitely unfit to eat by day.
(c)A loaf which the owner declared Chulin on Friday, and Hekdesh on Shabbos, can make a valid Eruv - because, since the food was Chulin on Friday, it has a Chezkas Chulin, which it retains on Shabbos; whereas if he first declared it Hekdesh on Friday, and Chulin (meaning redeemed) on Shabbos - it has a Chezkas Hekdesh when Shabbos enters, which will not fall away because of a Safek.
(d)When Rav Nachman said to Rava 'Lechi Teichol Aleih Kura de'Milcha', he meant to say - 'When you measure a Kur of salt and give it to me, I will tell you the reason.
(a)The Mishnah in Tevul-Yom rules that if, on Friday, a Tevul Yom declares Terumas Ma'aser when Shabbos enters, a jar of wine which he drew from a barrel of Ma'aser Rishon wine from which Terumas Ma'aser had not yet been separated - his declaration is effective. Why will this jar of wine not then be eligible for an Eruv? What does Rava prove from here?
(b)How does Rav Papa refute Rava's proof?
(a)Rava explains that a jar of wine which the Tevul-Yom declared Terumas Ma'aser on Friday to be effective when Shabbos enters, is not valid as an Eruv - because it is the end of the day (Friday evening) which acquires the Eruv, and at that time, the Eruv is still Tevel. He proves from here that it is the end of the day that acquires the Eruv, because, if it was the beginning, why would it not be valid, seeing as at that moment, the Terumas Ma'aser is effective, and it is no longer Tevel.
(b)Rav Papa contends that even if it is the beginning of the day that acquires the Eruv, the Eruv will not be valid. Why not? Because as we saw already earlier, the Eruv must be fit to eat by day, which is not the case here.
(a)Our Mishnah writes 'Masneh Adam al Eruvo ve'Omer "Im Ba'u Nochrim min ha'Mizrach (or 'min ha'Ma'arav'), Eruvo Eruv"'. Which basic principle does this Mishnah come to teach us?
(b)Which other case (other than that of 'Ba'u Nochrim') does the Tana insert?
(c)In which case does Rebbi Yehudah disagree with the Tana Kama, and what does he hold?
(d)Why does the Tana Kama argue with Rebbi Yehudah?
(a)The Mishnah of 'Masneh Adam al Eruvo ve'Omer "Im Ba'u Nochrim min ha'Mizrach (or 'min ha'Ma'arav'), Eruvo Eruv"' - is coming to teach us the principle of 'Yesh Bereirah'.
(b)Our Mishnah also speaks about a case of 'Ba Chacham' etc. - when one or two Chachamim came either in the east or in the west, and he wants to hear the Derashah of one of them.
(c)Rebbi Yehudah disagrees with the Tana Kama - in the case of two Chachamim, one in the east and one in the west, which the Tana Kama includes in Bereirah, irrespective of who the two Chachamim are; whereas Rebbi Yehudah maintains that, if one of the Chachamim is his Rebbe, then it is obvious that that was his intention from the outset, and that is where he should therefore go.
(d)The Tana Kama disagrees with this - In his opinion, it happens sometimes that a person wants to go and hear the other Rav, and not his own Rebbe (see Ya'avatz).
(a)Rav Yitzchak quotes a Beraisa which reverses both of the cases discussed in our Mishnah: i.e. when he specifically wishes his Eruv to take effect on the side where the gentiles are, and on the side where the Chacham is not. How do we reconcile the Beraisa with our Mishnah?
(a)With regard to a gentile: Our Mishnah is speaking about a gentile who comes to claim taxes, from whom one tends to run away; whereas the Beraisa is speaking about a gentile ruler, with whom he needs to plead. Since he requires his services, the Jew will be going to meet him, rather than to run away from him.With regard to a Chacham: Our Mishnah is speaking about a Chacham who is coming to Darshen, and he wants to go and hear him; whereas the Beraisa is speaking about a Talmid-Chacham who is coming to collect funds, and whom he therefore is trying to evade (Aruch - Rashi's explanation is very difficult to understand - Ya'avatz).
(a)Rav disregards our Mishnah in view of the opinion of Ayo, who quotes Rebbi Yehudah as saying that an Eruv that is made in two opposite directions, on the condition that in whichever direction the Chacham arrives, his Eruv should be valid, is not in fact, valid. Why not?
(b)Then why is it not considered 'Bereirah' even if the Eruv is only placed in one direction, on the condition that the Chacham arrives there?
(c)Rav preferred to disregard our Mishnah in face of Ayo, rather than vice-versa. This is on account of the Beraisa of 'ha'Loke'ach Yayin mi'Bein ha'Kutim' etc. What does Rebbi Yehudah say there, and how did that influence Rav?
(a)Ayo quotes Rebbi Yehudah as saying that an Eruv which is made in two opposite directions, on the condition that in whichever direction the Chacham arrives, his Eruv should be valid, is not in fact, valid - because he holds 'Ein Bereirah'.
(b)Ayo does not in fact, differentiate between two Chachamim in two directions or one Chacham who may come to the east or he may come to the west; either way, he holds 'Ein Bereirah'. When he says 'Im Ba Chacham le'Mizrach, Eruvo le'Mizrach' etc., he is referring to a case when the Chacham has already arrived, which is not a mater of Bereirah, since it is already known where the Chacham is, only he does not know yet (and a lack of knowledge is not called Bereirah).
(c)Rebbi Yehudah said, with regard to 'ha'Loke'ach Yayin' etc. - that if someone buys wine from among the Kutim (who are suspect of not separating Ma'asros from the produce that they sell to others), he is not permitted to declare the relevant Ma'asros first, and then to drink the wine, for the wine to take effect afterwards in retrospect (Bereirah). So it seems that Rebbi Yehudah holds 'Ein Bereirah', which bears out Ayo's statement, and contradicts our Mishnah.