This issue was discussed in our Insights to Eruvin 36:1. Enjoy!

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Eruvin 36

1) TECHUMIN D'ORAISA

QUESTION: The Gemara asks why Rebbi Yosi is lenient in a case of a doubt that involves Eruv Techumin (which is d'Rabanan), while he is stringent in a case of a doubt that involves Tum'ah d'Rabanan. The Gemara answers that Eruv Techumin is an enactment of the Rabanan that is not based on any law mid'Oraisa, while the enactments of Tum'ah d'Rabanan are based on the laws of Tum'ah mid'Oraisa.

The Rishonim point out that only the Techum of 2000 Amos is mid'Rabanan. The prohibition to walk more than 12 Mil (12 X 2000 Amos) on Shabbos, however, is forbidden mid'Oraisa (as is derived from the size of the encampment of the Jewish people in the wilderness; see RIF, end of first chapter of Eruvin, and RAMBAM, Hilchos Shabbos 27:1, based on the Yerushalmi). Since there is a concept of a Techum d'Oraisa, the enactment of Eruv Techumin has a source in the Torah. Why, then, does the Gemara say that it has no source in the Torah? (RASHBA, RITVA)

ANSWERS:

(a) The RASHBA and MAHARAL (Gur Aryeh, end of the first chapter of Eruvin) answer that even though there is a Techum d'Oraisa, the enactment of Eruv Techumin is not based on anything in the Torah. There is no instrument in the Torah that permits one to walk beyond the 12 Mil, nor does the enactment of Eruv Techumin enable people to walk beyond the Techum d'Oraisa.

(b) RAV GEDALYAH RABINOWITZ zt"l (of Manchester) in GIDULEI HEKDESH points out that the answer of the Rashba and Maharal seems to be subject to dispute. The RAMBAN (Eruvin 17b) writes that if the laws of Techumin are mid'Oraisa, then Eruv Techumin must also be d'Oraisa (either as a Halachah l'Moshe mi'Sinai or through logic ("Sevara")). The Ramban adds that according to the opinion that the Techum of 12 Mil is mid'Oraisa, there is also a Halachah l'Moshe mi'Sinai (or Sevara) that if one makes an Eruv for such a Techum, it permits him to walk another 12 Mil. Therefore, the concept of Eruv Techumin does exist mid'Oraisa.

Perhaps for this reason, the RA'AVAD (cited by the Rashba and Ritva) explains that the Gemara does not mean that there is no Techum mid'Oraisa. Rather, the Gemara means that the reason the Rabanan prohibited one to walk 2000 Amos is entirely unrelated to the Torah law of the 12-Mil Techum (because if their enactment was related to the Isur d'Oraisa of Techumin, then why did they choose to prohibit such a small fraction of the Torah's Techum?). In fact, the Rabanan inferred from the laws of the cities of the Levites (Eruvin 51a) that the boundaries of a city extend 2000 Amos beyond its walls. Therefore, they enacted that one may walk up to 2000 Amos from his place of Shevisah on Shabbos and Yom Tov.

(c) The RITVA writes that the Gemara means only that Rebbi Yosi maintains that there is no law of Techumin d'Oraisa at all. Other Tana'im, however, maintain that mid'Oraisa there is a Techum of 12 Mil.