Siman 415

One may only establish eruvei techumin for the purpose of a mitzvah. There is one who wishes to say that this applies to an eruv with bread, but with one's feet—one may establish an eruv even for a discretionary matter, (Beit Yosef and the Ri, beginning of chapter 8) and in a time of pressing need one may rely on this. (Eliyah Rabbah) And post facto, if one established an eruv for a discretionary matter, according to the opinion of the Bahag—it is not an eruv, and the Rambam in chapter 6 ruled—that it is an eruv, and the Rashba wrote to distinguish between one who establishes an eruv with bread and one who establishes an eruv with his feet, for with bread—his eruv is not an eruv, and with his feet—it is an eruv, (Beit Yosef) and our teacher, the Beit Yosef, ruled like the Rambam. And it is certain that when one established an eruv for the purpose of a mitzvah—he may go even for a discretionary matter. The reason that one may only establish an eruv for the purpose of a mitzvah is simple, for it is well understood that eruvei chatzerot and shitufei mevo'ot—this itself is a mitzvah, so that we do not stumble into the prohibition of carrying. But regarding techumin, it is not relevant to say it is to avoid coming to a prohibition, and it is only due to necessity. Therefore, for the need of a mitzvah they permitted it, and not for a discretionary matter. And in truth, the intention is not for an absolute mitzvah, but even when there is in this the delight of Shabbat and Yom Tov—it is also called a mitzvah, as will be explained, for in this the sages also saw fit to permit, because it is a mitzvah, "and you shall call the Shabbat a delight," and on Yom Tov we were commanded in joy.

Therefore, one may only establish an eruv in order to go to a house of mourning or to a wedding feast, or for a circumcision or other mitzvah, or to greet one's teacher or a friend who has arrived from a journey, or to oversee public affairs, or if one was outside his city and needs to go to his home, for it is a mitzvah to be with his wife and offspring. Our teacher, the Rema, wrote: "Or if one wishes to go for a stroll on Yom Tov or Shabbat in an orchard, in which there is joy and the like—it is called a matter of mitzvah" thus far his words, and this is for the reason we have explained. So too, because of fear, when one wishes to flee from oppressors or from bandits—it is a matter of mitzvah, and so too anything similar to this.

And even though regarding eruvei chatzerot one may establish the eruv ab initio during bein hashemashot, as is written in siman 393, nevertheless regarding eruvei techumin—one may not establish the eruv ab initio during bein hashemashot (Shabbat 34a), because this is a superior rectification, and they supported it with verses (Rashi); but ex post facto—his eruv is a valid eruv. Therefore, if two people said to him: "Go and establish an eruv for us," and for one he established the eruv while it was yet day, and for the other he established the eruv during bein hashemashot, and for this one for whom he established the eruv while it was yet day, his eruv was consumed during bein hashemashot, and for this one for whom he established the eruv during bein hashemashot, his eruv was consumed after dark—both of them have acquired the eruv. And the reason for this law has already been explained in siman 393, see there. However, there are those who disagree, and they hold that regarding techumin—even ex post facto it is not effective during bein hashemashot. (The opinion of Rabbeinu Tam in Tosafot ibid., and Rashi ibid. and the Rambam in chapter 6 ruled according to the first opinion.)

When one places eruvei techumin, he recites the blessing: "Who has sanctified us with His commandments and commanded us concerning the mitzvah of eruv. By means of this eruv, it shall be permitted for me to walk from such-and-such a place two thousand cubits in every direction." And if he makes an eruv for the public, he recites the blessing and also says: "By means of this eruv, it shall be permitted for so-and-so and so-and-so, etc." or he shall say: "it shall be permitted for all the residents of the city." And the blessing is not indispensable, but if he did not say "By means of this, etc." it is indispensable. (Magen Avraham, subsection 5) And even though regarding an eruv by foot one does not need to say anything, as I wrote in siman 410—this is because he is standing at the place of his dwelling. But regarding an eruv with bread, if he did not speak—by what matter is it recognizable that it is an eruv? And it appears to me that if he recited the blessing but did not say "By means of this," it is a valid eruv.