Techum Shabbos and Shabbos — Eruvin 52b
תלמוד בבלי מסכת עירובין דף נב/ב
אמר רבי חנינא רגלו אחת בתוך התחום ורגלו אחת חוץ לתחום לא יכנס דכתיב אם תשיב משבת רגלך רגלך כתיב
According to the Gemara here, when Yeshayahu HaNavi (58:13) comes to shore up the observance of Shabbos, he begins with the topic of Techum Shabbos. Why does he not begin with one of the more severe restrictions?
According to the Midrash (Bereishis Rabbah 11:7), the Torah alludes to Yaakov Avinu's Shemiras Shabbos by hinting at his observance of Techum Shabbos (Bereishis 33:18). Of all the aspects of Shabbos, why specifically Techum Shabbos?
According to Teshuvos HaRashba and Sefer HaEshkol, when the Gemara (Yoma 28b) states that Avraham Avinu kept the entire Torah, it says: "Even Eruvei Techumin" (based on Bereishis 26:5). Why specifically Techum Shabbos?
To answer these questions, R' Tzadok HaKohen of
It is for this reason that Meseches Shabbos begins with the laws of transferring objects (Hotza'ah) from domain to domain. And this is the underlying concept of Techum Shabbos. This is true of its Torah mandated scope of 12 mil, which alludes to the place of the encampment of the Jews in the Midbar (with its "Kedushas Machaneh" — see Bava Basra 75a). It is also true of the rabbinic scope of 2000 amos. This measure, explains Reb Tzadok, is based on the basic measure of four amos, which is the definition of a "space" even for negative ramifications — viz., distancing oneself while davening from excrement, etc. Since we know that something with positive ramifications is five-hundred-fold greater than something with negative ramifications (see Rashi to Shemos 34:7), a sacred space is five-hundred times greater than the space that can be the opposite — i.e., 2000 amos.
Yaakov Avinu was able to create sacred space even in Chutz La'Aretz, thus bequeathing to us the capacity to create similar space — through Shabbos — wherever we find ourselves (see Vayikra 23:3). It is for this reason that there is an explicit pasuk that alludes to Techum Shabbos in connection to him, while in connection to Avraham Avinu there is only a hint.