Mishneh Torah, Sabbath 28

Sugya Map: Iburei d'Ir (City Extensions)

• Issue: Determining the perimeter of a city for the purpose of the 2,000-cubit Sabbath limit.
• Nafka Mina: Whether a peripheral dwelling or structure functions as an extension of the city or as a point from which a new measurement begins.
• Primary Sources: Eruvin 55b-59a; Mishneh Torah, Sabbath 28.

Text Snapshot

Rambam states: "Whenever there is a home... 70 and 2/3 cubits or less from the city, it is considered part of the city... [and] the measurement begins from there" (Mishneh Torah, Sabbath 28:1).

• Leshon nuance: Note the precision: shibim amah u-shnayim shlish. This corresponds to the diagonal of a square of beit sa'atayim (5,000 sq cubits), the area of the Tabernacle courtyard.

Readings

• Ohr Sameach (ad loc.): Argues that the Rambam’s 70-cubit extension is rooted in the Tosefta and requires the city to be treated as a "square table" (tavla meruba'at). He notes that even a short city is augmented to reach this geometric standard for the corners.
• Maggid Mishneh: Challenges the interpretation of the measurement, noting that while Rambam is strict regarding what constitutes a "dwelling," he is uniquely lenient in aggregating these structures to extend the city boundary, effectively treating scattered dwellings as a unified urban entity.

Friction

• Kushya: If the 2,000-cubit limit is a Rabbinic institution, why does the Rambam enforce such rigid geometric requirements (square/compass directions) for city measurements?
• Terutz: The city boundary isn't merely a physical line; it is a halachic status of "inhabited space." By squaring the city, the Sages created a legal fiction that allows for uniform travel, preventing the chaos of measuring from irregular, organic borders.

Intertext

• Parallel: Shulchan Aruch, Orach Chayim 398:5 codifies this "square" approach.
• Responsa: Chatam Sofer, Orach Chayim 94 emphasizes that the "middle village" in a triangle must be mathematically aligned to count as an extension, reinforcing that iburei d'ir is a matter of geometric connectivity, not just proximity.

Psak/Practice

In contemporary hilchot techumin, we treat modern city limits (often defined by municipal boundaries or continuous housing) as the "city" for measurement purposes. However, the Rambam’s requirement for a "dwelling of 4x4 cubits" remains the litmus test for whether a peripheral structure extends the Techum.

Takeaway

The city boundary is not the wall, but the settlement; when we measure, we square the circle, transforming the organic sprawl of human habitation into a predictable, geometric zone of permission.