An Eruv Primer

This week’s parsha includes one of the major sources for prohibiting carrying on Shabbos, which provides a good opportunity to study some of the complicated halachos of carrying on Shabbos and the halachos of Eruvin. We cannot do justice to this vast and complicated topic in one short article. However, I will attempt to provide an introduction to some of the issues involved.

The Torah prohibits carrying from an enclosed area, called a “reshus hayachid,” to a public, non-enclosed area, a “reshus harabim,” or vice versa. It also prohibits carrying something for a distance of four amos (about seven feet) or more inside a reshus harabim. For our purposes, we will loosely define reshus hayachid as an area completely enclosed by walls, doors, or a combination of both, and a reshus harabim as an unenclosed area at least sixteen amos wide (about twenty-eight feet) meant for public use or thoroughfare. Many additional technical details define a reshus hayachid and a reshus harabim, some of which will be discussed later in this article.

A non-enclosed area that does not qualify as a reshus harabim is categorized as a “karmelis.” According to Torah law, one may carry inside, into and from a karmelis. However, Chazal ruled that a karmelis must be treated with the stringencies of both a reshus hayachid and a reshus harabim. This means that under most circumstances it is forbidden to carry inside, into, or from any area that is not completely enclosed. This is the way we are familiar with observing Shabbos – one does not carry in any unenclosed area. (I will later point out a significant halachic difference between a reshus harabim and a karmelis.)

Chazal also forbade carrying from one reshus hayachid to another when they are not owned by the same person. Thus, I may not carry on Shabbos from my house to my neighbor’s, even if both properties are completely enclosed. If both areas are owned by the same person, I may carry from one house to the other, as long as I don’t pass through an unenclosed area or an area owned by someone else. I may carry from my house to my neighbor’s if we make an “eruv” which allows the two areas to be treated as if they have common ownership.


The word eruv refers to several different conventions instituted by Chazal. We just mentioned the “eruv chatzeiros” that permits carrying between different areas that are enclosed but have separate ownerships. We create this eruv by making the property owners partners in a loaf of bread or a box of matzohs, which for these purposes is sufficient to consider the properties jointly owned. Once this eruv chatzeiros is made, one may carry from one residence within the eruv to another, since the eruv gives them common ownership. Common practice is to make the eruv with matzohs since they last a long time. Custom is to renew the eruv every Erev Pesach so that it is not forgotten.

One must make sure that the matzohs remain edible. I know of instances where the eruv was forgotten about and long afterwards it was discovered that the matzohs were no longer edible. Who knows how long people were carrying in a prohibited way because no one had bothered to check the matzohs!


Our discussion until now has been dealing with an area that is already fully enclosed. However, someone interested in carrying in an area that is not fully enclosed must close in the area before making an eruv chatzeiros. The most common usage of the word eruv is in reference to this enclosure.


The area must be completely enclosed by halachically acceptable “walls” and “doors.” Walls, buildings, fences, hills, and cliffs can all be used to enclose an area. However, when using structures and land features that already exist, invariably there will still be gaps between the structures that must be filled in to complete the enclosure.

The most common method to bridge the gaps is to make a “tzuras hapesach.” A tzuras hapesach vaguely resembles a doorway, consisting of two sideposts and a lintel that passes over them, which are the basic components of a doorway. According to halacha, a tzuras hapesach is considered a bona fide enclosure. Thus, if all gaps between the existing “walls” are “closed” with tzuros hapesach, the area is regarded as fully enclosed.

Some opinions allow small gaps to remain within the eruv’s perimeter without a tzuras hapesach. Many eruvin in North America rely upon this leniency, whereas in Eretz Yisrael the accepted practice is not to.


The halacha is that a planted field the size of 5000 square amos (approximately 14,000 square feet) within an enclosed area invalidates the ability to carry within the eruv. Similarly, an area of this size that is so overgrown that one would not walk through it will invalidate an eruv. This is a very common problem that is often overlooked. Although every responsible eruv has mashgichim to check the perimeters of the eruv, there is also a need to check periodically within the eruv to see that no large areas are being planted or have become this overgrown. I know of numerous instances where, unfortunately, this problem existed for a while before it was detected.


There are myriad details of how to make a tzuras hapesach, far more than can be detailed here. For example, most authorities accept the use of a wire for the lintel of a tzuras hapesach, although many opinions require it to be extremely taut (see Mishnah Berurah 362:66 and Shaar Hatziyun). Most eruvin use telephone wires as the “lintel” of the tzuras hapesach, although there are poskim who prohibit them (see Shu’t Yeshuos Malko, Orach Chaim #20). When telephone wires are used, posts or boards are placed directly below existing telephone wires, with care taken that the wire passes directly over the post. The lintel must pass directly above the sideposts, although the posts are not required to be tall enough to reach the “lintel” (Eruvin 11b). For example, if the wire used as lintel is twenty feet high and the side posts are only four feet tall, this is perfectly legitimate as long as the wire passes directly above the sideposts and that nothing intervenes between them. To guarantee that the wire remains above the posts, it is a good idea to use fairly wide “posts” and to periodically check that the wire is still directly above the posts. From personal experience I can tell you that as the posts or the telephone polls settle it is not unusual that they shift so that the post is no longer under the wire. This is also something that eruv mashgichim must periodically check but, unfortunately, often do not.

The tzuras hapesach is invalid if something intervenes in the gap between the top post and the side post. Thus, it is invalid to rest a side post against the side of a house and attach the top post to its roof, if any overhang of the roof extends below the lintel and above the side post. Similarly, the eruv is invalid if a sign intervenes between the sidepost and the wire being used as lintel.

I mentioned above that there is a major difference in halacha between a reshus harabim and a karmelis. A tzuras hapesach can only be used to enclose an area that is a karmelis where the prohibition against carrying is only rabbinic. It cannot be used to permit carrying in a reshus harabim where it is forbidden to carry min haTorah (Shulchan Aruch, Orach Chayim 364:2).

This leads us into our next discussion.


A strange phenomenon of hilchos eruvin is that although Chazal created the concept of eruv to facilitate peace among the Jewish people, probably no other mitzvah has been involved in so much controversy. Why is this?

The details of hilchos eruvin are extremely complicated and often subject to dispute. It is not unusual to find a situation where one rav forbids a certain eruv min HaTorah, while another rav rules that it is perfectly kosher. Although both decisions are based on the same Gemara and halacha, one posek condemns as chilul Shabbos what the other considers a mere chumrah or less.

This is not a new phenomenon. Let us share a halachic discussion that is over a thousand years old.

600,000 PEOPLE

There is a very old dispute whether a reshus harabim (min haTorah) only exists if the area is used by at least 600,000 people, just as the reshus harabim of Klal Yisrael in the desert was used by 600,000 people, the members of the Jewish nation. (Indeed, the question is raised that a reshus harabim should require several million people because the 600,000 count only men over twenty and did not include the women and children.)

Rashi (Eruvin 59a) writes that only an area with this number of people constitutes a reshus harabim that cannot be enclosed with a tzuras hapesach. This excludes all the towns and cities inhabited by Jews from the Middle Ages until fairly modern times. They did not have 600,000 people and could therefore be enclosed by a tzuras hapesach. However, many rishonim disagree with Rashi and rule that any street or marketplace sixteen amos wide is a reshus harabim and cannot be enclosed with a tzuras hapesach. This issue is made more confusing since the Shulchan Aruch in Orach Chayim 345:7 rules strictly, whereas in 303:18 he appears to rule leniently. Many major authorities follow the lenient interpretation (Magen Avraham; Taz in 345), and it was upon this basis that most Eastern European communities constructed eruvin. However, according to most authorities this lenience cannot be used as the basis to permit an eruv today since most large Jewish communities are in places with more than 600,000 people.


In the thirteenth century, Rav Yaakov ben Rav Moshe of Alinsiya wrote a letter to the Rosh explaining why he forbade a tzuras hapesach eruv in his town. In his response, the Rosh replied that Rav Yaakov’s concerns were groundless and that he should immediately construct an eruv. Subsequent correspondence reveals that Rav Yaakov did not change his mind and still refused to erect an eruv in his town. The Rosh severely rebuked him for this recalcitrance, insisting that if he (Rav Yaakov) persisted he would be placed in cherem. The Rosh also ruled that Rav Yaakov had the status of a zakein mamrei, a Torah scholar who rules against the decision of the Sanhedrin, which is a capital offense (Shu’t HaRosh 21:8)! All this demonstrates that heated disputes over eruvin are by no means a recent phenomenon.


Although there are many obvious advantages to having a kosher eruv, we should always be aware that there are also drawbacks. One major drawback is that people become unprepared if the eruv goes down one week. Suddenly, they cannot take their reading glasses to shul and their plans of pushing the stroller so they can eat the Shabbos meals at someone else’s house are disrupted.

Another disadvantage is that people become so used to having a eruv that they no longer pay serious attention to the prohibition against carrying. Children raised in such communities, and even adults who always lived in cities with an eruv, sometimes hardly realize that there is any prohibition against carrying.

In Israel, where virtually every town has an eruv, the assumption that there is always an eruv can be a tremendous disadvantage as the following story illustrates:

A moderately-learned frum Israeli moved to an American city with no eruv. He was hired by a yeshiva as cook and was responsible for the everyday kashrus of the yeshiva’s kitchen. The first Shabbos on his job, the new cook went for an afternoon stroll with his family, baby carriage and all. This raised a whirlwind in the yeshiva — people were shocked that they had entrusted the yeshiva’s kashrus to someone who openly desecrated Shabbos! Only later was it clarified that the cook was unaware that a city might not have an eruv. Living his entire life in cities with an eruv, he had automatically assumed that every city with a Jewish community had such a fixture!

In conclusion, we see that disputes among poskim over eruvin are not recent phenomena. In practice, what should an individual do? The solution proposed by Chazal for any such shaylah is “Aseh lecha rav, vehistalek min hasafek,” “Choose someone to be your rav, and remove yourself from doubt.” The rav can guide you to decide whether it is appropriate for you to carry within a certain eruv, after weighing factors including what heterim were used in the eruv’s construction, care of eruv maintenance and family factors. The psak and advice of one’s rav can never be underestimated!

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