In more than 200 cities around the world you can, if you look closely enough, find a thin wire that encircles a significant portion of the community. Most go about their days without even knowing it is there. If you happened to see it, there’s a good chance you just assumed it was a telephone or utility line and never gave it another thought. For those who are part of the Jewish community, however, that thin wire makes a world of difference — particularly on one day of the week.

The command to honor the Sabbath and keep it holy is found in Exodus 31:13-17. Among the ways the Sabbath is to be honored is by resting and doing no work. What constitutes “work” has been a matter of debate for millennia. For many Jews, particularly Orthodox Jews, it has been defined as “carrying a burden.” A burden might include one’s keys, wallet, or a baby stroller.

There is an exception to the rule against burden carrying. As long as the individual and the item remain within one’s private enclosure, it is not considered to be a violation of the Sabbath commandment. That’s where the nearly-invisible wire comes into play.

The wire is known as an eruv. It symbolically extends the private dwelling space of an individual or family to include everything that is within the space contained within the wire’s circumference. As long as one’s residence is within the confines of the eruv, he or she may safely leave home on the Sabbath without having to empty the pockets or leave the baby behind.

More than 200 cities claim an eruv. The largest is believed to be in Los Angeles. While most cities claim an eruv consisting of wire, the 80-square-mile area contained in the Los Angeles eruv is surrounded primarily by actual walls. The website for this eruv specifies what can and cannot be done on the Sabbath within this enclosure. It notes, for example, that it is impermissible to play ball, carry pets, stones, credit cards, car keys, or umbrellas. It is permissible, however, to push a baby stroller, carry a cane, handkerchief, rain hat, or house keys.

Maintaining the eruv is a serious business and can be quite costly. The eruv that surrounds most of the island of Manhattan consists of a clear fishing wire, but costs as much as $150,000 per year for upkeep and ensuring its integrity. Each Friday, a rabbi carefully inspects the perimeter, making sure there are no breaks or interference with the integrity of the eruv.

The establishment and maintenance of an eruv involve obtaining permission from public and private entities. In many cases, this is done through an informal grant of permission. Other situations make use of a legal easement. In some circumstances, it requires the acquisition of real estate. The logistics and costs associated with all of this are borne by the local congregations.

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