‘A City Is Given A Karpif’
If house stands less than 70 and 2/3 amos outside a city, it is considered an extension of the city and the techum – the 2,000 amos perimeter around a city beyond which one may not walk on Shabbos – is measured from that house.
R. Meir in our mishnah says that the techum of a city is not measured from the last house in a city, but rather from the city’s outskirts – its karpif – which is a perimeter of 70 and 2/3 amos of open space around the city and considered part of the city. Thus, one may walk a total of 2,070 and 2/3 amos outside a city on Shabbos.
A Matter of Continuity
The Sages disagree and maintain that the legal application of a karpif applies only in the instance of two neighboring cities. If two cities are within 70 and 2/3 amos of each other, they are considered one contiguous city and the residents of city A may walk 2,000 amos beyond city B (and vice versa). The halacha follows R. Huna who explains that each city is granted a space of 70 and 2/3 amos outside it. Thus, if the open space between the cities is no more than 141 and 1/3 amos – i.e. 2 x 70 and 2/3 amos – the two cities are considered one extended city.
The Rash (to our daf, 57a) cites the Maharam of Rothenberg who rules in accordance with R. Meir that the 2,000-amah techum of a city starts after its karpif (meaning that city residents are allowed to walk 2,000 amos plus an additional 70 and 2/3 amos beyond the city on Shabbos).
The Ritva (novella 57a) states that R. Meir only grants an extra 70 and 2/3 amos beyond the city itself, not beyond any isolated house standing outside the city. We measure from the city, not from the isolated house.
The Chazon Ish (110:19) draws a distinction between an occupied house and an abandoned house. He suggests that the Ritva is referring to an abandoned house. An occupied house, however, that stands within 70 and 2/3 amos of a city is considered part of the city proper and not merely an extension. Accordingly, we measure the techum starting 70 and 2/3 amos past any occupied house outside the city.
A Modern Application
Today many jurisdictions contain groups of continuous cities – each separately administered, with the open space between them measuring no more than 141 and 1/3 amos. In these jurisdictions, the halacha follows R. Huna and the residents of each city may walk 2,000 amos beyond the farthest city in each direction.