ביצה דף לז

דאית ליה אשה ובנים.

because it is dealing with a case in which he already has a wife and children, so that he has already fulfilled the mitzva to be fruitful and multiply, and his betrothal of another woman is only an optional act.

לא חולצין ולא מיבמין. והא מצוה קא עביד! לא צריכא, דאיכא גדול, ומצוה בגדול ליבם.

§ Nor perform ḥalitza, nor perform levirate marriage: The Gemara asks: But doesn’t one perform a mitzva through these acts? Why are they categorized as optional? The Gemara answers: No, it is necessary for the mishna to categorize them as optional, as it is speaking of a case when there is an older brother. Since the general principle is that the preferable way to carry out the mitzva is for the oldest brother to perform levirate marriage, the performance of levirate marriage by a younger brother is classified as optional.

וכלהו טעמא מאי — גזרה שמא יכתוב.

The Gemara clarifies the reason for the prohibition against judging, betrothing, etc., on Shabbat and Festivals: And in all these cases, what is the reason they may not be performed? It is a decree lest one write down the proceedings of these acts in a document, such as the verdict of a judgment, the document of betrothal, a document testifying to the ḥalitza, or a marriage contract in the case of levirate marriage.

ואלו הן משום מצוה: לא מקדישין ולא מעריכין ולא מחרימין — גזרה משום מקח וממכר.

§ It was taught in the mishna: And the following are notable because of the full-fledged mitzva involved in them, yet are prohibited on Shabbat: One may not consecrate, nor take a valuation vow, nor consecrate objects for use by the priests or the Temple. The Gemara explains: All these cases are prohibited because of a decree due to their similarity to commerce. These acts, which all involve the transfer of ownership to the Temple treasury, resemble commerce, which is prohibited on a Festival.

ולא מגביהין תרומות ומעשרות. פשיטא! תני רב יוסף: לא נצרכא אלא ליתנה לכהן בו ביום.

§ It was taught in the mishna: And one may not separate terumot and tithes. The Gemara asks: Is it not obvious that this is so? In doing so one makes forbidden food usable, a form of repairing, which is a prohibited labor. Rav Yosef taught: It is necessary for the mishna to teach this only to state that it is prohibited even to separate teruma in order to give it to a priest on the same day. One could have thought that since he is separating the produce in order to give it to a priest it should be permitted like any other preparation of food; the mishna therefore states explicitly that it is prohibited.

והני מילי פירי דטבילי מאתמול, אבל פירי דטבילי האידנא, כגון עיסה לאפרושי מינה חלה — מפרשינן ויהבינן לכהן.

The Gemara comments: And this applies only to produce that had the status of untithed produce, and therefore was required to be tithed, the day before the Festival. However, produce that became untithed now on the Festival itself, such as dough prepared on the Festival, which becomes untithed and requires ḥalla to be taken from it only after the dough is made: With regard to separating ḥalla from it, one may separate the ḥalla and give it to a priest even on a Festival.

והני, משום רשות איכא, משום שבות ליכא? והני, משום מצוה איכא, משום שבות ליכא?

The Gemara asks a question. When the mishna describes those cases as notable because they are optional, is this to say that their prohibition is not because of a rabbinic decree to enhance the character of Shabbat as a day of rest [shevut]? Likewise, with regard to those cases described as notable because they are mitzvot, is this to say that their prohibition is not because of shevut? The mishna, by referring only to the first of its three categories as shevut, implies that the acts listed in the following categories do not involve shevut. But this is not so; as the Gemara stated above, all these acts are prohibited by rabbinic decree to enhance the character of Shabbat and the Festival as days of rest.

אמר רבי יצחק, לא מבעיא קאמר: לא מבעיא שבות גרידתא דאסור, אלא אפילו שבות דרשות נמי אסור. ולא מבעיא שבות דרשות דאסור, אלא אפילו שבות דמצוה נמי אסור.

Rabbi Yitzḥak said: They are indeed all prohibited as shevut. The mishna lists three types of shevut: Those that involve no mitzva whatsoever, those that have a mitzva aspect to them, and those that constitute a full-fledged mitzva. And the tanna is speaking and arranges his list employing the style of: There is no need, i.e., he arranges the cases in order of increasing notability. First, there is no need to state, i.e., it is most obvious, that plain shevut, which involves no mitzva at all, is prohibited, but even shevut of an optional act, i.e., an act that is a minor mitzva, is also prohibited. And there is no need to state, i.e., it is obvious, that shevut of an optional act is prohibited, but even shevut of a full-fledged mitzva is also prohibited.

כל אלו ביום טוב אמרו, ורמינהו: משילין דרך ארובה ביום טוב, אבל לא בשבת!

§ It was taught in the mishna: The Sages spoke of all these acts being prohibited even with regard to a Festival; all the more so are they prohibited on Shabbat. There is no difference between a Festival and Shabbat except for work involving food. The Gemara raises a contradiction against this from an earlier mishna: One may lower produce from the roof into the house through a skylight to prevent it from being spoiled by the rain on a Festival, but not on Shabbat. This shows that there is another difference between a Festival and Shabbat besides food preparation: Doing a strenuous activity to prevent a loss is permitted on a Festival but prohibited on Shabbat.

אמר רב יוסף, לא קשיא: הא רבי אליעזר, הא רבי יהושע.

Rav Yosef said: This is not difficult, as this mishna here, which does not include the halakha of lowering produce as an example of a difference between Shabbat and a Festival, is in accordance with Rabbi Eliezer, whereas that previous mishna that does cite it as a difference is in accordance with Rabbi Yehoshua.

דתניא: אותו ואת בנו שנפלו לבור — רבי אליעזר אומר: מעלה את הראשון על מנת לשוחטו ושוחטו, והשני עושה לו פרנסה במקומו כדי שלא ימות.

Rav Yosef elaborates on his statement: As it is taught in a baraita: If a cow and her calf, which may not be slaughtered on the same day because of the biblical prohibition: “You shall not kill it and its offspring both in one day” (Leviticus 22:28), fell into a pit on a Festival, and their owner wishes to take them out, Rabbi Eliezer says: One may raise the first in order to slaughter it and then slaughter it, and as for the second, he provides it sustenance in its place so that it will not die in the pit. It is prohibited to undertake the strenuous task of raising an animal out of a pit except for the purpose of eating it on the Festival. Therefore, since one cannot slaughter both animals on the Festival, only one can be raised, while the other should be sustained in its place until after the Festival.

רבי יהושע אומר: מעלה את הראשון על מנת לשוחטו ואינו שוחטו, וחוזר ומערים ומעלה השני. רצה — זה שוחט, רצה — זה שוחט.

Rabbi Yehoshua, however, says: One may raise the first with the intent of slaughtering it and then change his mind and not slaughter it. Then he may go back and employ artifice by deciding that he prefers to slaughter the second one, and he raises the second. Having raised both animals, if he so desires he may slaughter this one; if he so desires he may slaughter that one. Rav Yosef understands the argument between the two Sages as follows: Rabbi Yehoshua maintains that it is permitted to perform a strenuous activity on a Festival in order to prevent a loss, and therefore he may raise both animals, lest the one left behind die in the pit. Rabbi Eliezer, on the other hand, holds that one may not perform a strenuous activity to prevent a loss, so the second animal must be left in the pit even though it may die there. It may therefore be posited that the mishna that permits lowering produce on a Festival to prevent loss is in accordance with Rabbi Yehoshua’s opinion. Rabbi Eliezer would disagree with this leniency, and the principle that there is no difference between Shabbat and a Festival other than food preparation would remain intact.

אמר ליה אביי: ממאי? דילמא עד כאן לא קאמר רבי אליעזר התם, אלא דאפשר בפרנסה, אבל הכא דלא אפשר בפרנסה — לא!

Abaye said to Rav Yosef: From where do you know that this analysis of these Sages’ opinions is correct? Perhaps Rabbi Eliezer stated his opinion that a strenuous activity to prevent monetary loss is prohibited on a Festival only thus far, there in the case of the animals in the pit, where it is possible to sustain the second animal in the pit and keep it from dying. But here, in the case of the produce on the roof, where there is no possibility of preventing the loss through providing sustenance, he would not prohibit lowering the produce to save it from loss.

אי נמי: עד כאן לא קאמר רבי יהושע התם, אלא דאפשר לאערומי. אבל הכא דלא אפשר לאערומי — לא.

Alternatively, one can propose an opposite argument: Rabbi Yehoshua stated his opinion that a strenuous activity to prevent loss is permitted only thus far, there in the case of the two animals, because it is possible to employ artifice to raise the second animal, so that an observer might assume that that he was not acting to preserve his property, but wished to eat the first animal and subsequently changed his mind. But here, in the case of the produce on the roof, where it is not possible to employ artifice, as it is clear that he is acting to salvage his produce, Rabbi Yehoshua would not be lenient. Therefore, Rav Yosef’s approach to resolving the contradiction has no support from this baraita.

אלא אמר רב פפא, לא קשיא: הא בית שמאי, הא בית הלל.

Rather, Rav Pappa said: This resolution of the contradiction is to be rejected in favor of the following: This is not difficult, as this case is in accordance with Beit Shammai, whereas that case follows the approach of Beit Hillel.

דתנן, בית שמאי אומרים: אין מוציאין לא את הקטן ולא את הלולב ולא את ספר תורה לרשות הרבים, ובית הלל מתירין.

As we learned in a mishna: Beit Shammai say: On a Festival one may not take out a child who cannot walk, nor a lulav, nor a Torah scroll into the public domain, as none of these are required for the preparation of food, and Beit Hillel permit it. It is certainly prohibited to carry out any item into the public domain on Shabbat, yet Beit Hillel permit it on a Festival. Therefore, it may be posited that just as Beit Hillel allow carrying out items on a Festival but not on Shabbat, so would they permit moving the produce off the roof on a Festival but not on Shabbat. According to Beit Shammai, who forbid carrying items out on a Festival and on Shabbat equally, moving the produce from the roof would also be equally prohibited, and the principle that there is no difference between Shabbat and a Festival other than food preparation would remain intact.

דלמא לא היא, עד כאן לא קא אמרי בית שמאי התם, אלא אהוצאה, אבל אטלטול — לא. אטו טלטול לאו צורך הוצאה הוא?

The Gemara at first refutes this explanation: Perhaps that is not so, as it is possible that Beit Shammai stated their opinion only thus far, there with regard to the prohibition against transferring objects from one domain to another, but not with regard to moving objects, such as produce, from place to place in the house. The Gemara rejects this claim: Is that to say that moving is not performed for the sake of taking out to the public domain? The decree against moving items unnecessarily, i.e., not for use on Shabbat or a Festival, was enacted due to a concern that one might take objects into the public domain. Rav Pappa’s explanation that it is only Beit Shammai who would prohibit lowering the produce from the roof therefore stands.

מתני׳ הבהמה והכלים כרגלי הבעלים. המוסר בהמתו לבנו או לרועה — הרי אלו כרגלי הבעלים.

MISHNA: The status of animals and vessels on Festivals is as the feet of their owner, meaning that one’s animals and vessels are governed by his own travel limitations on Shabbat and Festivals. In the case of one who delivers his animal to his son or to a shepherd before the Festival to care for it, these are as the feet of the owner, rather than those of the son or the shepherd.

כלים המיוחדין לאחד מן האחין שבבית — הרי אלו כרגליו. ושאין מיוחדין — הרי אלו כמקום שהולכין.

Vessels that have been inherited by several brothers and have not been divided among them but are still owned jointly, if they are designated for the use of one of the brothers in the house and the other brothers have no part in them, these are as his feet, and they are subject to his travel limitations. And as for those that are not designated for any particular brother, these are as a place where they may all go. They are limited by the travel limitations of every one of the brothers, as when one brother made a joining of Shabbat boundaries [eiruv teḥumin] and the others did not.

השואל כלי מחבירו מערב יום טוב — כרגלי השואל. ביום טוב — כרגלי המשאיל. וכן האשה ששאלה מחברתה תבלין ומים ומלח לעיסתה — הרי אלו כרגלי שתיהן.

One who borrows a vessel from another on the eve of a Festival, it is as the feet of the borrower rather than the owner, as when the Festival began the vessel established its place of rest in possession of the borrower. However, if he borrowed it on the Festival itself, it is as the feet of the lender, since at the start of the Festival its place of rest was established in the possession of its owner. And similarly, a woman who borrowed spices from another to put in a dish, or water and salt to put in her dough, these foods, i.e., the dish and the dough, which contain ingredients belonging to both parties, are as the feet of both of them; they are limited by the travel limitations of both parties. Rabbi Yehuda exempts one from travel limitations in the case of water, because it has no substance in the mixture and therefore is not considered connected to the original owner.

רבי יהודה פוטר במים, מפני שאין בהן ממש.

גמ׳ מתניתין

GEMARA: The Gemara asserts: The mishna

דלא כרבי דוסא, דתניא: רבי דוסא אומר, ואמרי לה: אבא שאול אומר, הלוקח בהמה מחברו מערב יום טוב, אף על פי שלא מסרה לו אלא

is not in accordance with the opinion of Rabbi Dosa. As it is taught in a baraita: Rabbi Dosa says, and some say Abba Shaul says: One who purchases an animal from another on the eve of a Festival, even if he did not deliver it to him until the Festival itself, it is as the feet of the purchaser. And one who delivers his animal to a shepherd, even if he did not deliver it to him until the Festival itself, it is as the feet of the shepherd. The mishna, on the other hand, teaches that an animal delivered to a shepherd remains as the feet of the owner, therefore apparently contradicting Rabbi Dosa.

ביום טוב — הרי היא כרגלי הלוקח. והמוסר בהמה לרועה, אף על פי שלא מסרה לו אלא ביום טוב — הרי היא כרגלי הרועה.

אפילו תימא רבי דוסא, ולא קשיא: כאן ברועה אחד, כאן בשני רועים. דיקא נמי דקתני: לבנו או לרועה, שמע מינה.

The Gemara rejects the assertion that this is a contradiction. You can even say that the mishna is in accordance with Rabbi Dosa, and it is not difficult. Here, in the baraita, it is referring to a town that has only one shepherd. In that case the owner knows with certainty beforehand that he will be delivering his animal to this shepherd over the course of the Festival, and therefore the animal’s place of rest is established as being identical to that of the shepherd. There, however, the mishna is referring to a town where there are two shepherds. Since the issue of which of them will receive this animal is undetermined when the Festival begins, the animal remains as the feet of its owner. The Gemara strengthens this assertion that the mishna is dealing with a case where there are two shepherds: The language of the mishna is also precise in accordance with this interpretation, as it teaches: To his son or to a shepherd, suggesting that initially he did not know to whom he would give the animal. The Gemara concludes: Indeed, learn from this that this is so.

אמר רבה בר בר חנה אמר רבי יוחנן: הלכה כרבי דוסא. ומי אמר רבי יוחנן הכי? והאמר רבי יוחנן: הלכה כסתם משנה, ותנן: הבהמה והכלים כרגלי הבעלים!

Rabba bar bar Ḥana said that Rabbi Yoḥanan said: The halakha is in accordance with the opinion of Rabbi Dosa, that animals given to a shepherd are as the feet of the shepherd. The Gemara asks: And did Rabbi Yoḥanan actually say this? But didn’t Rabbi Yoḥanan say a general principle that the halakha always follows an unattributed statement in a mishna? And we learned in the mishna: Animals and vessels are as the feet of the owner. One who delivers his animal to his son or to a shepherd, it is as the feet of the owner.

ולאו אוקימנא — כאן ברועה אחד, כאן בשני רועים!

The Gemara answers: And did we not establish that the baraita of Rabbi Dosa is dealing with a different case than the mishna, that here in the baraita it is dealing with a town with one shepherd, whereas there in the mishna it is dealing with a town with two shepherds? There is consequently no contradiction between establishing the halakha both in accordance with Rabbi Dosa and in accordance with the mishna.

תנו רבנן: שנים ששאלו חלוק אחד בשותפות, זה לילך בו שחרית לבית המדרש, וזה ליכנס בו ערבית לבית המשתה. זה ערב עליו לצפון, וזה ערב עליו לדרום.

§ The Sages taught: In the case of two people who borrowed one robe in partnership from a third party, this person in order to go to the study hall with it in the morning and that person in order to enter a wedding feast with it in the evening, and this one made a joining of Shabbat boundaries [eiruv teḥumin] for himself to the north in order to reach his destination, and that one made an eiruv for himself to the south in order to reach his destination, the one who made an eiruv for himself to the north may walk with the robe only to the north as far as it is permitted for the feet of the one who made an eiruv for himself to the south, i.e., he may go north only as far as the other borrower may go.

זה שערב עליו לצפון — מהלך לצפון כרגלי מי שערב עליו לדרום.

וזה שערב עליו לדרום — מהלך לדרום כרגלי מי שערב עליו לצפון.

And similarly, the one who made an eiruv for himself to the south may walk with the robe to the south only as far as is permitted for the feet of the one who made an eiruv for himself to the north, as the robe is as the feet of both borrowers and may go only as far as both of them may walk. If each of them placed his eiruv at a distance of one thousand cubits from their house, to the north and south respectively, they may each walk, without the robe, three thousand cubits from their regular dwelling-place, one partner toward the north and the other partner toward the south. The three thousand cubits are comprised of the thousand cubits from the house to the eiruv plus another two thousand, the standard Shabbat limit, from the location of the eiruv. The one whose eiruv is in the north may not wear the robe farther than one thousand cubits north of his house, as he would then be going beyond the farthest extent of the other’s Shabbat limit, and vice versa for the one whose eiruv is in the south.

ואם מצעו את התחום — הרי זה לא יזיזנה ממקומה.

And if they made their respective limits end in the center, i.e., if one placed his eiruv two thousand cubits from the house to the south, so that the house is his farthest limit to the north, and the other placed his eiruv two thousand cubits to the north of the house, the house being his farthest limit to the south, then each of them may not move the robe from its place at all.

אתמר: שנים שלקחו חבית ובהמה בשותפות, רב אמר: חבית מותרת ובהמה אסורה. ושמואל אמר: חבית נמי אסורה.

The Gemara records a dispute between amora’im. It was said: In the case of two people who purchased a barrel of wine or an animal in partnership before a Festival, in order to divide the contents of the barrel or the meat of the animal between them on the Festival itself, what is the halakha if the two people have different Shabbat limits? Rav said: The barrel is permitted to each of them, and each may take his portion on the Festival and transfer it within his respective Shabbat limit, which is also applicable to Festivals; but the animal is prohibited, and each portion of it may be transferred only within the limits that are shared by both purchasers. And Shmuel said: The barrel is also prohibited to be transferred beyond the limits shared by both people.

מאי קסבר רב? אי קא סבר יש ברירה — אפילו בהמה תשתרי! ואי קסבר אין ברירה — אפילו חבית נמי אסורה!

The Gemara questions the opinion of Rav, who distinguished between the case of the barrel and that of the animal. What does Rav hold? If he holds that there is retroactive designation, so that after the division of the barrel it becomes clarified retroactively which portion belonged to which partner, and the Festival place of rest for each portion is established at the start of the Festival in accordance with the person who will later become its owner, then even the animal should be permitted. And if he holds that there is no retroactive designation, so that at the start of the Festival both portions of the animal belong jointly to both of them and may therefore be transferred only within the limits shared by both people, then even the barrel should be prohibited.

לעולם קסבר יש ברירה, ושניא בהמה — דקא ינקי תחומין מהדדי. אמרי ליה רב כהנא ורב אסי לרב: לאיסור מוקצה לא חששו, לאיסור תחומין חששו?! שתיק רב.

The Gemara answers: Actually, the explanation for Rav is that he holds there is retroactive designation, and the reason Rav was stringent in the case of the animal is that an animal is different, as the limits absorb from each other. A live animal cannot be divided into two parts for ownership; each part of its body depends on and is nourished by the other. Consequently, even if the designation of the respective portions takes place retroactively, each portion continues to draw from the other part, so that at the time of division the two portions are once again mixed together. Rav Kahana and Rav Asi said to Rav: If that is your rationale, this indicates that the Sages were not concerned about the prohibition of muktze, as it is not assumed that each of them removed the portion of his partner from his mind, thereby prohibiting it from his own use, and yet they were concerned about the prohibition of Shabbat limits. Isn’t this illogical? Rav was silent and offered no response.

מאי הוי עלה? רבי הושעיא אמר: יש ברירה. ורבי יוחנן אמר: אין ברירה.

The Gemara asks: What conclusion was reached about this issue? Rabbi Hoshaya said: In general, there is retroactive designation, and they can therefore each transport their portions of both the barrel and the animal to their respective places. And Rabbi Yoḥanan said: There is no retroactive designation, and therefore they may not move their portions of either the barrel or the animal except within the limits shared by both of them.

וסבר רבי הושעיא יש ברירה? והתנן: המת בבית, ולו פתחים הרבה — כולן טמאים. נפתח אחד מהן — הוא טמא, וכולן טהורים. חשב להוציאו באחד מהן,

The Gemara asks: And does Rabbi Hoshaya really hold there is retroactive designation? But didn’t we learn in a mishna: If there is a corpse in a house that has many entrances, all the entrances are ritually impure, i.e., everything situated in the space of the entrance becomes impure, even in the part that lies beyond a closed door, separating it from the corpse. Since any of the entrances might be used to remove the corpse, and none are designated for that purpose, all are rendered impure. However, if one of them was subsequently opened, then the space of that particular entrance is impure, while all the others are pure, as it is assumed that that the corpse will be removed by way of the open door. Even if none of the entrances was actually open, if one merely intended to remove the corpse through a particular one of the entrances or through a window that is at least four by four handbreadths in size, this intention of his saves all the other entrances from impurity.

או בחלון שיש בו ארבעה על ארבעה — מצלת על הפתחים כולן.

בית שמאי אומרים: והוא שחשב עליו עד שלא ימות המת. ובית הלל אומרים: אף משימות המת.

The details of this last halakha are disputed by tanna’im. Beit Shammai say: And this applies only if he had this intention before the dead person died, so that at the time of death it was known which entrance would be used. And Beit Hillel say: It applies even if he had this intention only after the dead person died.

ואתמר עלה, אמר רבי הושעיא: לטהר את הפתחים מכאן ולהבא. מכאן ולהבא — אין, למפרע — לא.

And it is stated with regard to this mishna: Rabbi Hoshaya said: When Beit Hillel said that the other entrances are pure even if one thought of removing the corpse via a particular entrance only after the person died, they meant only to purify the entrances from that point and onward; from the moment of his intention there is no more impurity in the other entrances. From this the Gemara infers: From here and onward: Yes, the other entrances are saved from impurity, but retroactively: No. Whatever was in the doorways before this intent was formulated has already contracted ritual impurity and this cannot be reversed retroactively by one’s subsequent thoughts. This indicates that the principle of retroactive designation is not accepted by Rabbi Hoshaya.

אפוך, רבי הושעיא אמר: אין ברירה, ורבי יוחנן אמר: יש ברירה.

The Gemara resolves this contradiction in the following manner: Reverse the presentation of their opinions given above, and say: Rabbi Hoshaya said: There is no retroactive designation, and Rabbi Yoḥanan said: There is retroactive designation.

ומי אית ליה לרבי יוחנן ברירה? והאמר רב אסי אמר רבי יוחנן: האחין שחלקו — לקוחות הן, ומחזירין זה לזה ביובל.

The Gemara questions this resolution: And does Rabbi Yoḥanan really accept the principle of retroactive designation? But didn’t Rav Asi say that Rabbi Yoḥanan said: Brothers who divided property received as an inheritance are considered purchasers from each other, and as purchasers of land they must return the portions to each other in the Jubilee year, at which point they may redistribute the property? This demonstrates that Rabbi Yoḥanan does not hold that it is retroactively established that each brother’s portion was designated for him directly upon their father’s death, but rather it is considered that all the land was joint property until the brothers traded or bought their respective portions from each other.

וכי תימא: כי לית ליה לרבי יוחנן ברירה — בדאורייתא, אבל בדרבנן — אית ליה,

And if you should say: When does Rabbi Yoḥanan not accept the principle of retroactive designation? Only in regard to matters that are Torah law, but he does hold of retroactive designation in regard to matters of rabbinic law, such as the halakhot of Shabbat limits; this would account for the discrepancy.

ובדרבנן מי אית ליה? והתני איו —

But does he accept retroactive designation in matters of rabbinic law? Didn’t the Sage Ayo teach otherwise in regard to the halakhot of joining of Shabbat boundaries [eiruv teḥumin]? As it was taught in a mishna: One who has heard that a rabbi will be coming to a place near his town to deliver a lesson on Shabbat, but is unsure where the lecture will take place, may place two eiruvin on Shabbat eve in two different directions, while stipulating that only the eiruv on the side where the rabbi will teach will take effect. Furthermore, if he hears that two rabbis will be coming to two different locations, he may place two eiruvin and stipulate that he will decide on Shabbat which rabbi he prefers, and consequently which of the two eiruvin will take effect.

רבי יהודה אומר: אין אדם מתנה על שני דברים כאחד, אלא: אם בא חכם למזרח — עירובו למזרח, למערב — עירובו למערב, ואילו לכאן ולכאן — לא.

Ayo taught in a baraita that Rabbi Yehuda disagreed with this halakha and said: A person may not make a stipulation with regard to two contradictory things at once, and therefore if two Sages will be arriving, his condition is of no effect. Rather, it is true that in the first case, where he knows that a rabbi is coming but does not know from which direction, he may place two eiruvin and stipulate that if the rabbi comes from the east his eiruv in the east will take effect, and if the rabbi comes from the west, his eiruv in the west will take effect. However, in the second case, when two rabbis come to the two locations, one of them arriving here and the other arriving there, and one wants to place two eiruvin and decide on Shabbat which of the two lectures he will attend, this he may not do; that would require the identity of the functional eiruv to be determined retroactively, and one’s place of rest must be determined when Shabbat begins.