Carrying is one of the 39 categories of labor that are prohibited on Shabbat. Unlike some of the other categories of work, this one is explicitly prohibited in the Torah in connection to gathering manna on Shabbat (Exodus 16:29), and an example is given of someone who violates this prohibition by gathering wood on Shabbat (Numbers 15:32 as interpreted by Babylonian Talmud Shabbat 96b[1]). For this reason, the prohibition of carrying is said to be one of the basic prohibitions of Shabbat, which elevates its importance.
The prophet Jeremiah calls on the Israelites not to bring any burden into the gates of the city, implying that it is permissible to carry a burden within the city walls (Jeremiah 17:21). Later rabbinic tradition built on this idea to establish different categories of space or “domains,” most notably a “private domain” (reshut ha-yahid) such as a private house, a “public domain” (reshut ha-rabim) such as a public thoroughfare, and a domain that is neither private nor public (carmelit), which includes most other space. The prohibition on carrying on Shabbat was understood to prohibit moving an object from one domain to another. However, carrying an object within a private domain was allowed.
The rabbis taught that if a number of private domains were surrounded by a wall, the space thus enclosed “merged” the private domains with each other so that carrying would be allowed inside of that space. This “merged” space was called an eruv hatzerot (“merger of domains”); because this is the most common kind of eruv in halachah (Jewish law), it is often referred to simply as an eruv.[2] Within the eruv, carrying was allowed on Shabbat; outside of the eruv, carrying was prohibited on Shabbat.
When Jews lived in walled cities like Jerusalem and Tzfat, the walls of those cities made the area within them an eruv, so carrying was allowed within them on Shabbat. Now that Jews do not live in walled cities, the boundaries of an eruv can be created in a number of ways:
- Slope: Land that slopes at an incline can serve as a “wall” that marks the boundary of an eruv.[3]
- Power or telephone poles and lines: Poles and the lines attached to them can create the “form of a gate” (tzurat petah) that marks the boundary of an eruv.[4]
- Trees: Trees or tall bushes can create a “wall” that marks the boundary of an eruv in certain cases.
- Created poles and lines: In the absence of natural or previously man-made boundaries, a “wall” for an eruv can be created by setting up poles and stringing string along the poles. This is the most difficult option because it is subject to failure. For that reason, other forms of boundary are usually used to create the bulk of an urban eruv.
Because it is such a complex area of halachah, with many decisions to make, it is very difficult to create an eruv that every Jew will accept and hold by. Each Jewish community has to make its own decisions about how it creates an eruv and under whose authority and using which halachic decisions the eruv is created.
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[1] “Rav Yehuda said that Shmuel said: The wood gatherer [who was sentenced to death for desecrating Shabbat] was one who carried four cubits in the public domain.”
[2] Other kinds of eruv include eruv t’humim (“merger of borders”) to allow walking beyond the distance allowed to walk on Shabbat and eruv tavshilin (“merger of cooked foods”) to allow preparation of foods for Shabbat on a festival.
[3] Note that the boundary of the eruv is at the top of the slope.
[4] The rabbis taught that the “form of a gate” (tzurat petah) consisting of two upright poles and a “lintel” of the line between them can serve as a boundary for an eruv even though there is no “gate” that closes it. This reasoning follows from the idea that if there were a space surrounded by gates, the space would be defined even if all of the gates were open at the same time or even missing entirely.