40 Eiruvin 3/2-5

(2) We may make an eruv with demai [produce from which it is uncertain whether tithes were already taken]; and with ma'aser rishon [the first tithe of produce, which must be given to the Levi] from which terumah has been taken; and with ma'aser sheni and hekdesh [property, living or inanimate, devoted by its owner for sacred purposes, by which action he ceases to be its owner] which have been redeemed; and for Kohanim with challah [a portion of a batch of bread dough given to a Kohen which becomes holy upon separation, and can only be consumed by Kohanim or their household], and with terumah. But [we may] not [make an eruv] with tevel [produce from which the various tithes have not yet been separated]; and not with ma'aser rishon, from which terumah has not been taken; or with ma'aser sheni and hekdesh which have not been redeemed. If someone sends his eruv via the hand of a deaf-mute, a shoteh, a minor or one who does not acknowledge [the legal validity of] an eruv, it is not [considered] an eruv: but if he has told another person [not of the categories just mentioned] to receive it from [his messenger from those categories], behold it is [considered] an eruv.

(3) If he has put [his eruv] in a tree, if [the eruv was placed] higher than ten tefachim [a specific unit of length] [from the ground], it is not [considered] an eruv; [but if he puts it] lower than ten tefachim, it is [considered] an eruv. If he has put it into a pit, even if it is a hundred amot [a specific unit of length] deep, his eruv is [considered] an eruv. If he put it on the top of a cane or pole, in the case that it is detached [from actually growing in the ground but] is stuck [therein], even [if it is] a hundred amot high, behold it is [considered] an eruv. If he put it into a closet [which he locked] and lost the key, behold it is [considered] an eruv. Rabbi Eliezer says, "If he does not know that the key is in its place, it is not [considered] an eruv."

(4) If the eruv rolled out of the techum [the area around a person or community within which it is permissible to travel on Shabbat], or if a heap [of stones] fell on it, or if it got burned, or if [it was] terumah and became impure; [if any of these happen] while [it is] yet day, [before the Shabbat comes in], it is not [considered] an eruv; [but if it happens] after it got dark, behold it is [considered] an eruv. If there is a doubt [about the time when it happened], Rabbi Meir and Rabbi Yehuda say, "This is [like at once driving] an ass [and leading a] camel [which make the person get stuck between them]." Rabbi Yose and Rabbi Shimon say, "An eruv about which there is a doubt is [considered] valid." Rabbi Yose further said, "Avtulmos testified, in the name of five elders, that an eruv about which there is a doubt is [considered] valid."

(5) A man may make his eruv conditional and say, "If [hostile] gentiles come from the east, my eruv [shall extend my techum] to the west; [if they come] from the west, my eruv [shall extend my techum] to the east; if they come from both directions, I [will be permitted to] go to the place [direction] that I want; [if] they don't come from either direction, I am like [the rest of] my townsmen [concerning the preexisting techum]; should a sage come from the east, my eruv [shall extend my techum] to the east; [should one come] from the west, my eruv [shall extend my techum] to the west; [if one] come from each direction, I [will be permitted to] go to the place [direction] that I want; [if] none [come] from either direction, I am like the rest of my townsmen [concerning the preexisting techum]." Rabbi Yehuda says, "If one of them [the two sages who come] was his teacher, he goes to his teacher; and if both were his teachers, he [will be permitted to] go to the place [direction] that he wants."