Eruvin Chapter 8

אֵין מַנִּיחִין שְׁנֵי עֵרוּבִין אֶחָד בַּמִּזְרָח וְאֶחָד בַּמַּעֲרָב כְּדֵי שֶׁיְּהַלֵּךְ בְּמִקְצָת הַיּוֹם עַל אֶחָד מִשְׁנִי הָעֵרוּבִין וּבִשְׁאָר הַיּוֹם עַל הָעֵרוּב הַשֵּׁנִי. שֶׁאֵין מְעָרְבִין שְׁנֵי עֵרוּבִין לְיוֹם אֶחָד. טָעָה וְעֵרֵב לִשְׁתֵּי רוּחוֹת כִּמְדֻמֶּה הוּא שֶׁמְּעָרְבִין לִשְׁתֵּי רוּחוֹת. אוֹ שֶׁאָמַר לִשְׁנַיִם צְאוּ וְעָרְבוּ עָלַי אֶחָד עֵרֵב עָלָיו לַצָּפוֹן וְאֶחָד עֵרֵב עָלָיו לַדָּרוֹם מְהַלֵּךְ כְּרַגְלֵי שְׁנֵיהֶם:

One may not deposit two eruvin - one in the west and one in the east - so that one will be able to walk for a portion of the day [in the direction of] one of the eruvin, and to rely on the second eruv for the remainder of the day. [The rationale is that] one may not make two eruvin for a single day. If a person erred, and established two eruvin in two different directions, because he thought that this was permitted, or he told two people to establish an eruv for him, and one established an eruv to the north and one established an eruv to the south, he may walk only in the area common to both of them.

כֵּיצַד מְהַלֵּךְ כְּרַגְלֵי שְׁנֵיהֶם. שֶׁאֵינוֹ יָכוֹל לְהַלֵּךְ אֶלָּא בְּמָקוֹם שֶׁיֵּשׁ לִשְׁנֵיהֶם לְהַלֵּךְ בּוֹ. נָתַן הָאֶחָד עֵרוּב בְּרִחוּק אֶלֶף אַמָּה לְרוּחַ מִזְרָח וְהִנִּיחַ הַשֵּׁנִי מֵהֶן עֵרוּבוֹ בְּרִחוּק חֲמֵשׁ מֵאוֹת אַמָּה לְרוּחַ מַעֲרָב. אֵין זֶה שֶׁעֵרְבוּ עָלָיו מְהַלֵּךְ בַּמַּעֲרָב אֶלָּא אֶלֶף אַמָּה כְּרַגְלֵי מִי שֶׁעֵרֵב עָלָיו בַּמִּזְרָח. וְלֹא יְהַלֵּךְ בַּמִּזְרָח אֶלָּא אֶלֶף וַחֲמֵשׁ מֵאוֹת אַמָּה כְּרַגְלֵי מִי שֶׁעֵרֵב עָלָיו בַּמַּעֲרָב. לְפִיכָךְ אִם עֵרֵב אוֹ עֵרְבוּ עָלָיו שְׁנֵי עֵרוּבִין אֵלּוּ אֶחָד בְּרִחוּק אַלְפַּיִם אַמָּה לַמִּזְרָח וְאֶחָד בְּרִחוּק אַלְפַּיִם אַמָּה לַמַּעֲרָב הֲרֵי זֶה לֹא יָזוּז מִמְּקוֹמוֹ:

What is meant [by the expression], "he may walk only in the area common to both of them"? That he may walk only in the area that is within [the Sabbath limits] of both of these locations. [For example,] if one [of his agents] deposited an eruv 1000 cubits to the east [of his city's periphery] and the other deposited an eruv 500 cubits to the west, the person for whom the eruvin were deposited may walk only 1000 cubits to the west, as would be permitted [the agent] who established the eruv in the east, and 1500 cubits to the east, as would be permitted [the agent] who established the eruv in the west. Therefore, if one established an eruv 2000 cubits to the east and the other established an eruv 2000 cubits to the west, the person may not move from his place.

מְעָרֵב אָדָם שְׁנֵי עֵרוּבִין בִּשְׁתֵּי רוּחוֹת וּמַתְנֶה וְאוֹמֵר אִם אֵרַע לִי דְּבַר מִצְוָה אוֹ נִלְחַצְתִּי לְמָחָר וְנִצְרַכְתִּי לְרוּחַ זוֹ זֶה הָעֵרוּב הוּא שֶׁאֲנִי סוֹמֵךְ עָלָיו וְהָעֵרוּב שֶׁבָּרוּחַ הַשֵּׁנִית אֵינוֹ כְּלוּם. וְאִם נִצְרַכְתִּי לְרוּחַ זוֹ הַשֵּׁנִית זֶה הָעֵרוּב הוּא שֶׁאֲנִי סוֹמֵךְ עָלָיו וְשֶׁבָּרוּחַ הָרִאשׁוֹנָה אֵינוֹ כְּלוּם. וְאִם נִצְרַכְתִּי לִשְׁתֵּי הָרוּחוֹת יֵשׁ לִי לִסְמֹךְ עַל אֵיזֶה עֵרוּב שֶׁאֶרְצֶה וּלְאֵיזֶה שֶׁאֶרְצֶה אֵלֵךְ. וְאִם לֹא אֵרַע לִי דָּבָר וְלֹא נִצְרַכְתִּי לְרוּחַ מֵהֶן אֵין שְׁנֵי הָעֵרוּבִין הָאֵלּוּ עֵרוּב וְאֵינִי סוֹמֵךְ עַל אֶחָד מֵהֶן אֶלָּא הֲרֵינִי כִּבְנֵי עִירִי שֶׁיֵּשׁ לוֹ אַלְפַּיִם אַמָּה לְכָל רוּחַ מִחוּץ לַחוֹמָה:

It is permissible for a person to establish two eruvin in two opposite directions and make the [following] stipulation: "If tomorrow there is a mitzvah or a necessity that arises and requires me to walk in this direction, then it is this eruv that I am relying upon, and the other eruv is of no consequence. If, by contrast, it is necessary that I go to the other direction, the eruv [in that direction] is the one on which I will rely, and the first eruv is of no significance. "If I am required to go in both directions, I may rely on whichever of the eruvin I desire, and thus go in whichever direction I desire. If nothing [out of the ordinary] arises, and I am not required to go in either direction, neither of the eruvin is of consequence, nor do I rely on them. Instead, my situation is the same as that of any other inhabitant of my city, and I may proceed two thousand cubits in all directions from the city's wall."

כְּשֵׁם שֶׁאָסוּר לָצֵאת חוּץ לַתְּחוּם בְּשַׁבָּת כָּךְ אָסוּר לָצֵאת בְּיוֹם טוֹב וּבְיוֹם הַכִּפּוּרִים. וּכְשֵׁם שֶׁהַמּוֹצִיא מֵרְשׁוּת לִרְשׁוּת בְּשַׁבָּת חַיָּב כָּךְ הַמּוֹצִיא מֵרְשׁוּת לִרְשׁוּת בְּיוֹם הַכִּפּוּרִים חַיָּב. אֲבָל בְּיוֹם טוֹב מֻתָּר לְהוֹצִיא מֵרְשׁוּת לִרְשׁוּת. לְפִיכָךְ מְעָרְבִין עֵרוּבֵי חֲצֵרוֹת וּמִשְׁתַּתְּפִין בַּמְּבוֹאוֹת לְיוֹם הַכִּפּוּרִים כְּשַׁבָּת. וּמְעָרְבִין עֵרוּבֵי תְּחוּמִין לְיוֹם הַכִּפּוּרִים וּלְיָמִים טוֹבִים כְּדֶרֶךְ שֶׁמְּעָרְבִין לְשַׁבָּת:

Just as it is forbidden to proceed beyond a city's [Sabbath] limits on the Sabbath, so too, it is forbidden to proceed beyond those limits on the holidays and on Yom Kippur. Just as a person who transfers an article from one domain to another on the Sabbath is liable, so too, a person who transfers an article from one domain to another on Yom Kippur is liable. On the holidays, by contrast, it is permitted to transfer articles from one domain to another. Therefore, eruvin should be established in courtyards and shitufim should be established in lanes for Yom Kippur, as they are established for the Sabbath. Similarly, eruvei t'chumin may be established for Yom Kippur and the holidays as they are established for the Sabbath.

יוֹם טוֹב שֶׁחָל לִהְיוֹת סָמוּךְ לְשַׁבָּת בֵּין מִלְּפָנֶיהָ בֵּין מִלְּאַחֲרֶיהָ אוֹ שְׁנֵי יָמִים טוֹבִים שֶׁל גָּלֻיּוֹת יֵשׁ לוֹ לְעָרֵב שְׁנֵי עֵרוּבִין לִשְׁתֵּי רוּחוֹת וְסוֹמֵךְ עַל אֵי זֶה מֵהֶן שֶׁיִּרְצֶה לַיּוֹם הָרִאשׁוֹן וְעַל הָעֵרוּב שֶׁבָּרוּחַ הַשְּׁנִיָּה לַיּוֹם הַשֵּׁנִי. אוֹ מְעָרֵב עֵרוּב אֶחָד לְרוּחַ אַחַת וְסוֹמֵךְ עָלָיו לְאֶחָד מִשְּׁנֵי יָמִים וּבַיּוֹם הַשֵּׁנִי יִהְיֶה כִּבְנֵי הָעִיר וּכְאִלּוּ לֹא עָשָׂה עֵרוּב וְיֵשׁ לוֹ אַלְפַּיִם אַמָּה לְכָל רוּחַ. בַּמֶּה דְּבָרִים אֲמוּרִים בִּשְׁנֵי יָמִים טוֹבִים שֶׁל גָּלֻיּוֹת אֲבָל בִּשְׁנֵי יָמִים טוֹבִים שֶׁל רֹאשׁ הַשָּׁנָה הֲרֵי הֵן כְּיוֹם אֶחָד וְאֵינוֹ מְעָרֵב לִשְׁנֵי יָמִים אֶלָּא לְרוּחַ אַחַת:

[The following rules apply to] a holiday that occurs next to the Sabbath - whether before it or after it - or to the two days of a holiday as observed in the diaspora: A person may establish two eruvin in two opposite directions and rely on either for the first day, and the other for the second day. Similarly, he may establish a single eruv in one direction and rely on it for one of the two days, and on the other day consider himself like the other inhabitants of the city - i.e., it is as if he did not made an eruv, and thus he is entitled to proceed two thousand cubits in all directions [from the city's periphery]. When does this apply? To the two days observed as holidays in the diaspora. Regarding the two days of Rosh HaShanah [different rules apply]. They are considered to be a single [extended] day, and one may establish an eruv in one direction alone for both these days.

וְכֵן מַתְנֶה אָדָם עַל עֵרוּבוֹ וְאוֹמֵר עֵרוּבִי לְשַׁבָּת זוֹ אֲבָל לֹא לְשַׁבָּת אַחֶרֶת. אוֹ לְשַׁבָּת אַחֶרֶת אֲבָל לֹא לְשַׁבָּת זוֹ. לְשַׁבָּתוֹת וְלֹא לְיָמִים טוֹבִים לְיָמִים טוֹבִים וְלֹא לְשַׁבָּתוֹת:

Similarly, a person who [deposits] an eruv [t'chumin] may make [any of the following] stipulations: "On this Sabbath, my eruv shall be in effect, but not on another Sabbath," or "On another Sabbath [my eruv shall be in effect], but not on this Sabbath." [Similarly, he may stipulate that the eruv shall be in effect] on the Sabbaths but not on holidays, or on holidays and not on Sabbaths.

אָמַר לַחֲמִשָּׁה הֲרֵינִי מְעָרֵב עַל אֵיזֶה מִכֶּם שֶׁאֶרְצֶה רָצִיתִי אֵלֵךְ לֹא רָצִיתִי לֹא אֵלֵךְ. אַף עַל פִּי שֶׁרָצָה מִשֶּׁחָשְׁכָה יֵלֵךְ. דָּבָר שֶׁהוּא מִדִּבְרֵי סוֹפְרִים יֵשׁ בּוֹ בְּרֵרָה. וְכֵן הַמְעָרֵב לְשַׁבָּתוֹת שֶׁל כָּל הַשָּׁנָה וְאָמַר רָצִיתִי אֵלֵךְ לֹא רָצִיתִי לֹא אֵלֵךְ אֶלָּא אֶהְיֶה כִּבְנֵי עִירִי כָּל שַׁבָּת שֶׁיִּרְצֶה יֵלֵךְ אַף עַל פִּי שֶׁרָצָה מִשֶּׁתֶּחְשַׁךְ:

When a person tells five others, "I am establishing an eruv on behalf of one of you, whom I will choose [later]. If I choose, that person will be able to go. If I do not choose, he will not be able to go." Even if this person chooses [a companion] after nightfall, he may go. For the principle of b'reirah appliesregarding a matter of Rabbinic law. Similarly, a person may establish an eruv for all the Sabbaths of the year and stipulate, "If I desire [to rely on the eruv], I may go, and if I do not desire [to rely on it], I may not go - and I will be [governed by the same rules] as the other inhabitants of my city." He may go on whichever Sabbaths he desires, even if he does not make the decision to go until after nightfall.

הַמְעָרֵב לִשְׁנֵי יָמִים טוֹבִים שֶׁל גָּלֻיּוֹת אוֹ לְשַׁבָּת וְיוֹם טוֹב אַף עַל פִּי שֶׁהוּא עֵרוּב אֶחָד לְרוּחַ אַחַת לִשְׁנֵי הַיָּמִים צָרִיךְ שֶׁיִּהְיֶה הָעֵרוּב בִּמְקוֹמוֹ מָצוּי בְּלַיִל הָרִאשׁוֹן וּבְלֵיל שֵׁנִי כָּל בֵּין הַשְּׁמָשׁוֹת. כֵּיצַד הוּא עוֹשֶׂה. מוֹלִיכוֹ בְּעֶרֶב יוֹם טוֹב אוֹ בְּעֶרֶב שַׁבָּת וּמַחְשִׁיךְ עָלָיו וְנוֹטְלוֹ בְּיָדוֹ וּבָא לוֹ אִם הָיָה לֵיל יוֹם טוֹב. וּלְמָחָר מוֹלִיכוֹ לְאוֹתוֹ מָקוֹם וּמַנִּיחוֹ שָׁם עַד שֶׁתֶּחְשַׁךְ וְאוֹכְלוֹ אִם הָיָה לֵיל שַׁבָּת אוֹ מְבִיאוֹ אִם הָיָה לֵיל יוֹם טוֹב. מִפְּנֵי שֶׁהֵן שְׁתֵּי קְדֻשּׁוֹת וְאֵינָן כְּיוֹם אֶחָד כְּדֵי שֶׁנֹּאמַר מִלֵּיל רִאשׁוֹן קָנָה הָעֵרוּב לִשְׁנֵי יָמִים:

One who makes an eiruv techumin (the placing of food in a location to extend the area to which one is permitted to walk on the Sabbath, a holiday, or the Day of Atonement) for a two-day holiday in the Diaspora or for the Sabbath and [an adjacent] holiday, although it is one eiruv in one direction for both days, the eiruv-food must be in its place on the first night and the second night for the entire period between sundown and nightfall. What does he do? He brings the eiruv-food on the eve of the holiday or of the Sabbath and waits with it until dark and takes it with him if it is the night of a holiday (on which carrying is permitted in certain circumstances). The next day, he takes it to the same place and leaves it there until nightfall and eats it if it is the Sabbath or takes it with him if it is a holiday. This is because the Sabbath and the holiday are two [separate] periods of holiness and are not considered to be one day; therefore, we are not able to say that the eiruv works from the first day for both days.

נֶאֱכַל הָעֵרוּב בָּרִאשׁוֹן קָנָה הָעֵרוּב לָרִאשׁוֹן וְאֵין לוֹ עֵרוּב לַשֵּׁנִי. עֵרֵב בְּרַגְלָיו בָּרִאשׁוֹן צָרִיךְ לְעָרֵב בְּרַגְלָיו בַּשֵּׁנִי וְהוּא שֶׁיֵּלֵךְ וְיַעֲמֹד בְּאוֹתוֹ מָקוֹם וְיַחֲשֹׁב בְּלִבּוֹ שֶׁיִּקְנֶה שָׁם שְׁבִיתָה. עֵרֵב בְּפַת בָּרִאשׁוֹן אִם רָצָה לְעָרֵב בְּרַגְלָיו בַּשֵּׁנִי הֲרֵי זֶה עֵרוּב. וְאִם רָצָה לְעָרֵב בְּפַת צָרִיךְ לְעָרֵב בְּאוֹתָהּ הַפַּת עַצְמָהּ שֶׁעֵרֵב בָּהּ בָּרִאשׁוֹן:

If the eiruv-food was eaten on the first day, the eiruv was acquired for the first day, and there is no eiruv for the second day. If he made the eiruv with his feet on the first day, he must make it with his feet on the second day, this being walking to the place and standing there, thinking that he should acquire a place of rest there [such that the place where he is standing will be considered his place so he can walk 2000 cubits in any direction from that place]. If he made the eiruv with bread on the first day, and he makes it with his feet the second day, it is an acceptable eiruv. If he wants to make the eiruv with bread [the second day], he must use the same bread that he used for the eiruv the first day.

יוֹם הַכִּפּוּרִים שֶׁחָל לִהְיוֹת עֶרֶב שַׁבָּת אוֹ לְאַחַר שַׁבָּת בִּזְמַן שֶׁמְּקַדְּשִׁין עַל פִּי הָרְאִיָּה יֵרָאֶה לִי שֶׁהֵן כְּיוֹם אֶחָד וּקְדֻשָּׁה אַחַת הֵם:

If the Day of Atonement falls on the evening of the Sabbath or the night following the Sabbath during the time that the months were decided on the basis of people witnessing the new moon, it seems to me that they are considered to be one day and one period of holiness.

זֶה שֶׁאָמַרְנוּ שֶׁיֵּשׁ לוֹ לְעָרֵב שְׁנֵי עֵרוּבִין בִּשְׁתֵּי רוּחוֹת לִשְׁנֵי הַיָּמִים וְהוּא שֶׁיִּהְיֶה אֶפְשָׁר לוֹ לְהַגִּיעַ לְכָל אֶחָד מִשְּׁנֵי הָעֵרוּבִין בַּיּוֹם הָרִאשׁוֹן. אֲבָל אִם אִי אֶפְשָׁר לוֹ לְהַגִּיעַ לָעֵרוּב שֶׁל יוֹם הַשֵּׁנִי בַּיּוֹם הָרִאשׁוֹן אֵין עֵרוּב הַשֵּׁנִי עֵרוּב. שֶׁהָעֵרוּב מִצְוָתוֹ שֶׁיִּהְיֶה בַּסְּעֻדָּה הָרְאוּיָה מִבְּעוֹד יוֹם וְזֶה הוֹאִיל וְאֵינוֹ יָכוֹל לְהַגִּיעַ לְזֶה הָעֵרוּב בַּיּוֹם הָרִאשׁוֹן הֲרֵי זוֹ אֵינָהּ רְאוּיָה מִבְּעוֹד יוֹם:

This that we said that he can make two eiruvs in two directions for two days [of a holiday] is only if he is able to get to each of the two eiruv-foods on the first day. But if he is unable to get to the eiruv-food for the second day on the first day, the second eiruv is not an eiruv. [This is] because the commandment of the eiruv-food is that it should be able to be eaten as a meal while it is still [the] day [i.e. not the night, of the Sabbath or holiday], and in this case, because he can not get to the second eiruv-food on the first day, it is not fit for eating while it is still day.

כֵּיצַד. הֲרֵי שֶׁהִנִּיחַ עֵרוּבוֹ בְּרִחוּק אַלְפַּיִם אַמָּה מִבֵּיתוֹ לְרוּחַ מִזְרָח וְסָמַךְ עָלָיו לְיוֹם רִאשׁוֹן וְהִנִּיחַ עֵרוּב שֵׁנִי בְּרִחוּק אַמָּה אַחַת אוֹ מֵאָה אוֹ אֶלֶף בְּרוּחַ מַעֲרָב וְסָמַךְ עָלָיו לְיוֹם שֵׁנִי אֵין זֶה הַשֵּׁנִי עֵרוּב. שֶׁהֲרֵי בַּיּוֹם הָרִאשׁוֹן אֵין זֶה הָעֵרוּב הַשֵּׁנִי רָאוּי לוֹ מִבְּעוֹד יוֹם לְפִי שֶׁאֵינוֹ יָכוֹל לְהַגִּיעַ אֵלָיו שֶׁהֲרֵי לֹא נִשְׁאַר לוֹ בְּרוּחַ מַעֲרָב כְּלוּם:

How so? If he left the eiruv-food 2000 cubits to the east of his house and designated it for the first day and left another eiruv-food 1, 100, or 1000 cubits west [of his house], this second eiruv is not an eiruv. For behold, on the first day, the second eiruv-food was not fitting for him while it was still day because he was not able to get to it because he could not walk to the west of his house at all [because the eiruv-food of the first day established his rest place 2000 cubits east of his house so the farthest west he could have walked was his house].

אֲבָל אִם הִנִּיחַ עֵרוּבוֹ בְּרִחוּק אֶלֶף וַחֲמֵשׁ מֵאוֹת אַמָּה מִבֵּיתוֹ בְּרוּחַ מִזְרָח וְסָמַךְ עָלָיו לְיוֹם רִאשׁוֹן וְהִנִּיחַ עֵרוּב שֵׁנִי רָחוֹק מִבֵּיתוֹ לְרוּחַ מַעֲרָב בְּתוֹךְ חֲמֵשׁ מֵאוֹת אַמָּה וְסָמַךְ עָלָיו לְיוֹם שֵׁנִי הֲרֵי זֶה עֵרוּב. שֶׁהֲרֵי אֶפְשָׁר לוֹ שֶׁיַּגִּיעַ לוֹ בַּיּוֹם הָרִאשׁוֹן:

But if he left his eiruv-food 1500 cubits east of his house and designated it for the first day and left a second eiruv-food no more than 500 cubits west of his house and designated it for the second day, it is an eiruv. [This is] because he is able to get to it on the first day.

יוֹם טוֹב שֶׁחָל לִהְיוֹת בְּעֶרֶב שַׁבָּת אֵינוֹ עוֹשֶׂה עֵרוּב בְּיוֹם טוֹב לֹא עֵרוּבֵי חֲצֵרוֹת וְלֹא עֵרוּבֵי תְּחוּמִין אֶלָּא מְעָרֵב הוּא בְּיוֹם חֲמִישִׁי שֶׁהוּא עֶרֶב יוֹם טוֹב. וְאִם חָלוּ שְׁנֵי יָמִים טוֹבִים שֶׁל גָּלֻיּוֹת בַּחֲמִישִׁי וְעֶרֶב שַׁבָּת מֵעֶרֶב מִיּוֹם רְבִיעִי עֵרוּבֵי תְּחוּמִין וְעֵרוּבֵי חֲצֵרוֹת. וְאִם שָׁכַח וְלֹא עֵרֵב הֲרֵי זֶה מְעָרֵב עֵרוּבֵי חֲצֵרוֹת בַּחֲמִישִׁי וּבְעֶרֶב שַׁבָּת וּמַתְנֶה אֲבָל לֹא עֵרוּבֵי תְּחוּמִין:

[In the case of] a holiday that falls on the eve of the Sabbath, he may not make an eiruv chatzeirot [to permit carrying within a courtyard] or eiruv techumin [to permit walking beyond 2000 cubits from his house]; instead, he makes it on Thursday, which is the eve of the holiday. And if the two days of a holiday in the Diaspora fell on Thursday and the eve of the Sabbath, he can make an eiruv chatzeirot and eiruv techumin on Wednesday. If he forgot and did not make an eiruv [then], he can make an eiruv chatzeirot on Thursday and stipulate a condition [see below], but not an eiruv techumin.

כֵּיצַד מַתְנֶה. אוֹמֵר בַּחֲמִישִׁי אִם הַיּוֹם יוֹם טוֹב אֵין בִּדְבָרַי כְּלוּם וְאִם לָאו הֲרֵי זֶה עֵרוּב. וּלְמָחָר חוֹזֵר וּמְעָרֵב וְאוֹמֵר אִם הַיּוֹם יוֹם טוֹב כְּבָר עֵרַבְתִּי מֵאֶמֶשׁ וְאֵין בִּדְבָרַי הַיּוֹם כְּלוּם וְאִם אֶמֶשׁ הָיָה יוֹם טוֹב הֲרֵי זֶה עֵרוּב. בַּמֶּה דְּבָרִים אֲמוּרִים בִּשְׁנֵי יָמִים טוֹבִים שֶׁל גָּלֻיּוֹת אֲבָל בִּשְׁנֵי יָמִים טוֹבִים שֶׁל רֹאשׁ הַשָּׁנָה הֲרֵי הֵן כְּיוֹם אֶחָד וְאֵינוֹ מְעָרֵב לָהֶן אֶלָּא מֵעֶרֶב יוֹם טוֹב: סָלִיק הִלְכוֹת ערוּבִין

How does he stipulate a condition? He says on Thursday, 'If today is the holiday, my words [making an eiruv] lack substance and if it is not [a holiday], this is an eiruv.' The next day, he makes an eiruv again and says, 'If today is the holiday, I already made an eiruv yesterday, and my words lack substance, and if yesterday was the holiday, it is an eiruv.' When does this apply? On the two days of a holiday in the Diaspora, but the two days of the New Year are considered as one day, and he may make an eiruv only on the eve of the holiday.

The End of the Laws of eruvs.