זמנים
הלכות עירובין
פרק ח

Halacha

הלכה א
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:
כסף משנה
1.
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.1This principle is based on the following concept: Since an eruv t'chumin establishes a particular location as a person's place for the Sabbath, only one such place can be established, and not two.
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.

הלכה ב
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:
כסף משנה
2.
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.

הלכה ג
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:
כסף משנה
3.
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.2As the Maggid Mishneh mentions, this halachah is dependent on the concept that in cases of Rabbinic law, the principle of b'reirah applies. Thus, retroactively it is considered that at the commencement of the Sabbath, the person had the intent of establishing an eruv in the direction that he was eventually required to proceed.
"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."

הלכה ד
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:
כסף משנה
4.
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.3See Tzafenat Paneach (in his gloss on Hilchot Shabbat 27:1), who states that the Rambam considers the limits on travel on the holidays and on Yom Kippur as Rabbinic in origin. In support, he cites the Rambam's statements in Hilchot Sanhedrin, Chapter 19, regarding the negative commandments punishable by lashing: "A person who goes beyond the [Sabbath] limits on the Sabbath, a person who performs a forbidden labor on a holiday."
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.4The liability incurred by the violator is somewhat different. A person who willfully performs any of the Sabbath labors is liable for execution, while one who violates a forbidden labor on Yom Kippur is liable only for karet. (See Hilchot Sh'vitat Asor 1:2.) On the holidays, by contrast, it is permitted to transfer articles from one domain to another.5See Hilchot Sh'vitat Yom Tov 1:4, which states that since the prohibition against the forbidden labor of transferring articles was lifted on the holidays regarding the preparation of food, it was lifted entirely.
Therefore, eruvin should be established in courtyards and shitufim should be established in lanes for Yom Kippur, as they are established for the Sabbath.6See Maggid Mishneh and the Mishnah Berurah 416:31, which mention opinions that see a benefit in the establishment of eruvin in courtyards on the holidays as well. Similarly, eruvei t'chumin may be established for Yom Kippur and the holidays as they are established for the Sabbath.

הלכה ה
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:
כסף משנה
5.
[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.7Although for a single Sabbath one may not establish eruvin in two opposite directions, this rule does not apply when the Sabbath and a holiday follow one another. The Sabbath and the holidays represent two different expressions of holiness (Eruvin 38b). Therefore, the location defined as one's "place" - and thus an eruv established - for one does not necessarily apply regarding the other.
Similarly, regarding the two days of the holidays observed in the diaspora: in essence, the holidays were to be observed for only one day. The observance of a second day was instituted only because of uncertainty regarding the calendar. (See Hilchot Kiddush HaChodesh 5:4-5.) Therefore, the two days are also considered to be separate entities.
The Ra'avad suggests qualifying the Rambam's statements. The Rambam, however, appreciated the problem that he raised and clarified the issue in Halachah 12.
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 city8This also involves a redefinition of one's place. Instead of its being considered to be the location of the eruv, it is considered to be one's home. - 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,9Since these two days were observed as a holiday even in Eretz Yisrael when the moon was sanctified on the basis of the testimony of witnesses (Hilchot Kiddush HaChodesh 5:7), they are considered to be a single expression of holiness. Eruvin 39b refers to them as "one long day," and the halachic requirements that apply to one day apply also to the other. and one may establish an eruv in one direction alone for both these days.10See the notes on Halachah 8 with regard to whether or not it is necessary for the eruv to remain in its place for both nights of the holiday.

הלכה ו
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:
כסף משנה
6.
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],11The food deposited for the eruv must exist at beyn hash'mashot and be fit to eat. This is particularly important in the summer months, when it is possible that the eruv has become stale or has been eaten by vermin (Mishnah Berurah 416:9). 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.

הלכה ז
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:
כסף משנה
7.
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 applies12Ordinarily, a person must establish his eruv before nightfall. Nevertheless, since he made a stipulation beforehand, we rely on the principle of b'reirah, and we say that retroactively it is considered to be as if he decided to rely on the eruv before nightfall (Maggid Mishneh).regarding a matter of Rabbinic law.13For other examples of the Rambam's rulings concerning this matter, see Hilchot Sh'vitat Yom Tov 5:20, Hilchot Terumah 1:21, Hilchot Ma'aser 7:1, and Hilchot Ma'aser Sheni 4:15.
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.

הלכה ח
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:
כסף משנה
8.
[The following rule applies] when a person establishes an eruv for the two days of a holiday as observed in the diaspora or for a Sabbath and a holiday [that are celebrated consecutively]: Even when the person establishes a single eruv in one direction for both days, the eruv must be accessible14If the eruv is not accessible - even if it is present in its designated location - it is not acceptable, as stated in Chapter 6, Halachot 8 and 12. in its [designated] location on both the first and second nights throughout [the period of] beyn hash'mashot.
What should he do? He should take [the eruv to the desired place] on the eve of the Sabbath or on the eve of the holiday, and wait until nightfall. He may then take it in his hand and carry it away, if it is a holiday.15The Maggid Mishneh explains that the removal of the eruv is merely a suggestion offered, lest a person leave the eruv in its place, and it be destroyed by vermin or the like. In a place where the eruv will surely be preserved, there is no point in removing it. Needless to say, on the Sabbath, when it is forbidden to carry, and it is forbidden to remove the eruv, this suggestion does not apply.
If one leaves the eruv in the designated place and there is a possibility that it will be destroyed, one is required to go to that place on the following day to check that it still exists (Mishnah Berurah 416:14).
On the following day, he should take it16The Be'ur Halachah 416 asks: Since it is possible to establish the eruv by walking to the designated location (as stated in the following halachah), of what value is it that the person carried the food with him? The Be'ur Halachah explains that in this instance, we are speaking about a person who has an agent establish the eruv for him. Therefore, it is necessary for him to use food. to the same location,17The eruv must be deposited in the same location; otherwise, this is forbidden. Were one to change either the location (or the food used for the eruv), one would have been considered as either preparing on the Sabbath for a holiday, or on a holiday for the Sabbath (Shulchan Aruch, Orach Chayim 416:2). deposit it there until nightfall and eat it18There is no obligation to eat it. The Rambam's intent is merely that from this time onward, there is no obligation that the eruv remain intact (Mishneh Berurah 416:15). if it is Friday night, or take it with him if it is the night of a holiday.
[This is necessary, for] they are two different expressions of holiness, and are not considered to be a single [extended] day with regard to which it would be possible to say on the first night that one established the eruv for both days.19The Rambam's statement implies that on Rosh HaShanah, it is necessary to establish an eruv only on the first night of the holiday. Even if the eruv is consumed before the beginning of the second day, it is acceptable, just as it would be acceptable for the entire Sabbath, even if it had been consumed after beyn hash'mashot.
The Ra'avad objects to this ruling. He maintains that the distinction of the two days of Rosh HaShanah as a single "extended" day applies only as a stringency, but not as a leniency. Therefore, the eruv established before the first night must remain in its place on the second night as well.
The Maggid Mishneh justifies the Rambam's view, bringing supports that indicate that our Sages' definition of these two days as "one long day" brings about a leniency as well as a stringency. The Mishnah Berurah 416:11 follows the Rambam's ruling.

הלכה ט
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:
כסף משנה
9.
[In the situation described in the previous halachah,] were the eruv to be eaten on the first day, it is effective for the first day, but the person [may not establish] an eruv [with food] for the second day.
If he established an eruv by walking [to the desired location] on the first day, he may establish an eruv for the second day only by walking to the same location20He may not establish the eruv by depositing food, for this would involve the performance of an activity on either the Sabbath or the holiday for the benefit of the other. As mentioned, it is forbidden to prepare on the Sabbath for a holiday or on a holiday for the Sabbath (Shulchan Aruch, Orach Chayim 416:2). and making the resolution21He may not make a verbal statement, for this would be considered to be preparation for the coming day (ibid.). that he is establishing this as his "place" for the day.
If he established an eruv with bread on the first day [he has two options]: If he desires to establish an eruv by walking [to the desired location] on the second day, the eruv is acceptable. If he desires to establish an eruv by depositing a loaf of bread, [he may,] provided he uses the same loaf of bread that he used the first day.22Since he uses the same loaf, he is not considered to be performing a new activity; this location had already been established as his "place," and he is merely perpetuating the existing situation. If he brought a different loaf, it would be considered to be preparing for the coming day (ibid.).

הלכה י
יוֹם הַכִּפּוּרִים שֶׁחָל לִהְיוֹת עֶרֶב שַׁבָּת אוֹ לְאַחַר שַׁבָּת בִּזְמַן שֶׁמְּקַדְּשִׁין עַל פִּי הָרְאִיָּה יֵרָאֶה לִי שֶׁהֵן כְּיוֹם אֶחָד וּקְדֻשָּׁה אַחַת הֵם:
כסף משנה
10.
When Yom Kippur [would] fall on Friday or on Sunday during the era when the sanctification [of the moon] was dependent on its being sighted] by witnesses,23According to the fixed calendar we follow at present, it is impossible for Yom Kippur to fall on either Sunday or Friday. (See Rosh HaShanah 20a.) it appears to me24This expression implies a ruling for which the Rambam has no explicit source in the Talmud, but which he arrived at through a process of deduction. that [the two days] are considered to be one [extended] day25Rabbi Akiva Eiger explains that this also implies a leniency. As indicated by the conclusion of Halachah 8, there is no need to establish an eruv on the second day. and are considered to be one continuum of holiness.26The rationale is that all the prohibitions that apply on the Sabbath also apply on Yom Kippur (Maggid Mishneh).

הלכה יא
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:
כסף משנה
11.
The statement made previously27In Halachah 5. that a person may establish two different eruvin in two directions for two days applies only when it is possible for the person to reach both of the eruvin on the first day [without departing from his Sabbath limits]. If, however, it is impossible on the first day for him to reach the eruv for the second day, the eruv for the second day is invalid.28Note the gloss of the Sefer HaKovetz on Halachah 5, which discusses whether the law in this halachah applies only with regard to a holiday and a Sabbath that follow consecutively, or also with regard to the two days of a holiday that are observed in the diaspora. The Magen Avraham 416:3 rules that the restrictions apply with regard to the two days observed in the diaspora as well.
[The rationale is that] the mitzvah of eruv [can be fulfilled only] with a meal that is fit to be eaten while it is still day. Since the person may not reach the eruv [intended for the second day] on the first day [because it is beyond his Sabbath limits], it is not considered to be a meal that is fit to be eaten while it is still day.

הלכה יב
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:
כסף משנה
12.
What is implied? If a person deposited an eruv two thousand cubits eastward of his home and relied on it for the first day [he is forbidden to walk westward at all].29See Chapter 6, Halachah 4. [Therefore,] if he deposited an eruv one cubit, one hundred cubits, or one thousand cubits to the west and relied on it for the second day, the second eruv is invalid.
[The rationale is that] the second eruv is not fit for him on the first day, for he may not reach it, since he is not able to proceed toward the west at all.

הלכה יג
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:
כסף משנה
13.
If, however, he deposited his eruv one thousand five hundred cubits eastward of his home and relied on it for the first day, and deposited a second eruv within five hundred cubits to the west of his house and relied upon it for the second day, the eruv is valid. For it is possible for him to reach it on the first day.

הלכה יד
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:
כסף משנה
14.
When a holiday falls on a Friday, it is forbidden to establish an eruv [for the Sabbath] on the holiday: neither an eruv chatzerot nor an eruv t'chumin.30For it is forbidden to prepare for the Sabbath on a holiday. (See the Mishnah Berurah 393:1, which questions whether or not an eruv established on a holiday in error is acceptable.)
Note also the Or Sameach, which explains that, according to the Rambam, it is forbidden to establish an eruv t'chumin on the first day of a holiday for the second day. (This ruling runs contrary to a decision of the Noda BiY'hudah (Vol. II, Responsum 48).
Instead, one should establish the eruv on Thursday, the day prior to the holiday.
If the two days celebrated as a holiday in the diaspora fall on a Thursday and a Friday, one should establish both an eruv chatzerot and an eruv t'chumin on Wednesday. If a person forgot, and did not establish an eruv beforehand, he may establish an eruv chatzerot in a conditional manner on Thursday and Friday.31In Hilchot Sh'vitat Yom Tov 6:14-15, when discussing the establishment of an eruv tavshilin and other similar matters, the Rambam states that in the present era, we may not make such a conditional arrangement. This leniency was granted only in the era when the establishment of the calendar was dependent on the testimony of witnesses, and the second day of a holiday was observed because of a doubt concerning the day on which the holiday should be celebrated. At present, there is no such doubt, and the second day is celebrated because of a Rabbinic decree requiring us to preserve the previous custom. (See Hilchot Kiddush HaChodesh 5:5.)
Other authorities (see the gloss of the Ra'avad on Hilchot Sh'vitat Yom Tov) take issue with the Rambam on this point; it is their view that is accepted as halachah in the Shulchan Aruch (Orach Chayim 393:1).
He may not, however, do this with regard to an eruv t'chumin.32Beitzah 17a explains why a distinction is made between these two types of eruvin. By establishing an eruv t'chumin, a person designates a place as his home for the Sabbath, and our Sages would not permit this to be done on a holiday. In contrast, the establishment of an eruv chatzerot negates one's ownership. Therefore, greater leniency is shown.

הלכה טו
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
כסף משנה
15.
What is implied? On Thursday, the person should make the following stipulation:33Note the Birkei Yosef (Orach Chayim 528), which states that a blessing should not be recited. "If today is a holiday, my statements are of no consequence. But if not, this should be [accepted as] an eruv."
On the following day, he should again establish the eruv34The Mishnah Berurah 393:6 suggests using the same loaf of bread. Otherwise, it would be necessary to keep both loaves until the Sabbath.and say, "If today is a holiday, I have established my eruv yesterday, and my statements today are of no consequence. If, however, yesterday was the holiday, this should be [accepted as] an eruv."
When does the above apply? To the two days observed as holidays in the diaspora. The two days of Rosh HaShanah, by contrast, are considered to be one [extended] day. Therefore, with regard to them, it is possible to establish an eruv only on the day prior to the holiday.
(Blessed be God who grants assistance.)

זמנים הלכות עירובין פרק ח
Zemanim Eruvin Chapter 8