Calculating the Eiruv's Techum

Eiruvin (5:7) | Yisrael Bankier | 2 years ago

As discussed in last week's issue, one is not allowed to travel outside the city at distance of greater than two thousand amot. If one needed to travel for the purpose of a mitzvah further in one direction, then they can place an eiruv techum to one side of the city. Doing so moves their makom shevitah (dwelling place) to that location, enabling them to walk two thousand amot in each direction from that point. The Mishnah (5:7) explains that "what he gains [in one direction] he loses [in the other]. We shall try to understand this Mishnah.

The Bartenura explains by way of example. If the eiruv techum was placed one thousand amot west of the city, it would enable the individual to walk three thousand amot in that direction. The individual therefore gains one thousand amot west. If the width of the city itself is one thousand amot (or less), then we treat the entire city as if it is four amot and he could only travel one thousand amot east of the city. The thousand amot the individual gains in the west, he lost in the east. Importantly however, if the city was wider than one thousand amot such that the two thousand amot east of the eiruv reaches a point in the middle of the city, then the person would only be able to walk until that point. The Shulchan Aruch (408:1) rules like this understanding of the Mishnah.

The Tosfot R' Akiva Eiger notes that according to the Bartenura the Mishnah must be according to R' Yehuda who maintaines (4:5) that one has four amot in each direction around the eiruv, after which one measures the two thousand amot. That would then explain why one has one thousand amot to the east in our example above, despite the (small) city is itself being considered four amot. Indeed, the Shulchan Aruch explains that one would have only nine hundred and ninety-six amot to travel in the east in the case above.

The Tosfot (60b, s.v ein) however quote the Mahari who explains that if the person who setup the eiruv techum sleeps in his house in the city, then the city is considered like four amot. In other words, even if the two thousand amot only reached the center of the city, the person would be able to walk throughout the city. The Ritva, who also cites the Mahari, explains that if that were not the case, someone living in the center of a large city, would never be able to use an eiruv techum.

Note that according to this understanding, there is still a difference if the two thousand amot reach the center of the city or encompassed the city. In the former case, while the personal may walk the entire city, they would not be able to work any further (using our example) to the east of the city. The Rama rules that one can be lenient like this opinion. How do we understand this leniency?

The Chaye Adam (77:3) explains that were it not for this leniency, and one's house was further than two thousand amot from where the eiruv was located, then he would not be able to return to reach his own house. He explains that that result would not be considered "darchei no'am" (pleasant way) about which the Torah is described. In other words, due to a rabbinic decree one would need to move out of his home for Shabbat. Consequently, the Chachamim built into the laws of eiruv techum that the city in which one sleeps is considered like four amot such that he can walk around the entire city.

The Chazon Ish (109:16) however explains that wherever one intended to eat and sleep is his real main dira (residence). The law of eiruv techum was instituted to give the person the ability to shift their techum to center around a different makom shevitah. Nevertheless it does not come at the cost of losing his city.

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