“On Shabbat, every person must remain in his residence,” said Moshe to the people, forbidding them to walk more than a certain distance beyond their desert encampment. This distance, which measures two thousand amot – about two thirds of a mile – is known as techum Shabbat. It is the same distance that stretched from the perimeters of the Levite cities to their outlying suburbs.
These are the biblical sources on which the rabbis rely when prohibiting one from walking beyond the techum Shabbat. One may walk up to 2,000 amot in any direction from one’s residence on Shabbat, but not beyond. The “beyond the techum” prohibition applies both on Shabbat and Yom Tov, as well as on Yom Kippur. It does not, however, apply in any area that can be legally defined as a reshut hayachid, a private domain, including an area that has been transformed into a reshut hayachid by means of an enclosure – an eruv.
What constitutes a person’s residence from which the 2,000 amot are measured? That depends on where the person finds himself at the onset of Shabbat. If he finds himself in a walled or otherwise enclosed city, the 2,000 amot is measured from the city walls irrespective of the size of the city. Accordingly, a person can walk on Shabbat tens upon tens of miles to the city walls and then another 2,000 amot. If he finds himself at the onset of Shabbat in a city without walls, the 2,000 amot is measured from the end of the city.
For this purpose, a city is defined as any place that has at least three streets with at least two permanent houses in each street. The “end of the city” is that point at which one house is more than 70 amot (between 105 feet and 140 feet) away from the next house. Accordingly, on Shabbat a person can walk through country villages until he reaches the last house within 70 amot of the previous one and then another 2,000 amot.
What happens if one wants to attend a synagogue, visit a friend or just take a Shabbat stroll beyond the techum Shabbat? One may do so by performing a ceremony called “eruvei techumin.” This ceremony allows one to walk a total of 4,000 amot in one chosen direction by symbolically moving one’s point of residence at the onset of Shabbat 2,000 amot in the direction one wishes to walk on Shabbat. However, these additional 2,000 amot that one may now walk on Shabbat in one chosen direction are not free. One has traded them for the 2,000 amot one could have walked in the opposite direction had one not performed eruvei techumin.
There are two ways to conduct the eruv ceremony. One method is to travel before Shabbat to a point not more than two thousand amot from one’s original residence, remain there until after twilight, bein hashmashot, and then walk home. This point then becomes one’s new symbolic residence. The following day, Shabbat, one may walk back to one’s symbolic residence plus an additional 2,000 amot from there.
The alternative, and most commonly used, method is for the person or his agent to place a sufficient amount of food for two meals at a point not more then 2,000 amot from one’s original residence before Shabbat. At that point and time, one articulates one’s intention to acquire that place as one’s new symbolic residence. One then makes the eruv blessing and returns home, this time before bein hashmashot. This point then becomes one’s new symbolic residence. This alternative method of eruvei techumin, once performed, is valid for all Shabbatot of the year, provided, however, that the food remains at the symbolic residence and remains edible. For this purpose matzot can be used.
May a person who has boarded a ship before Shabbat sail beyond the techum on Shabbat? This question is left unresolved in tractate Eruvin. It depends on whether the law, which provides that a public domain ends at the height of ten tefachim above the ground for the purpose of carrying on Shabbat, also applies for the purpose of walking beyond the techum on Shabbat. If it does, then one may sail beyond the techum because the hull of a ship is typically more than ten tefachim above the bed of the sea, so that one is not deemed to be traveling in a reshut harabim.