Dear Aaron,

Thanks for your excellent question. The conclusion of the Gemara on 48a is that with regard to Techumin, we measure "b'Amah Didei", which means each individual measures the distance from the tip of his middle finger until his elbow, and uses that for an Amah. In the event that a person's arm is not proportionate to the rest of his body, he uses a standard Amah of six Tefachim. So your assumption is somewhat correct: when using a standard Amah for Techumin, we use an amah of six Tefachim since it is an Isur d'Rabanan. This is also the ruling of the Shulchan Aruch 349:1 and 396:1.

Kol tuv,

Y. Landy

Hello again.

Once again an excellent question. The Sha'ar Hatziyun (396:3) quotes the Gaon Ya'akov who explains that this case is an exception to the rule. The reason is that in the case of the Posuk "Shevu Ish Tachtov" from which we derive the dimensions of four Amos (48a), the Gemara explains that for a person to move an item around, he needs a spacious four Amos, thus it is only in this case that we have room for leniency. Other cases, even m'd'Rabanan, have the stringent Amah.

I would like to suggest another possibility. In the case of Movui, it is indeed d'Rabanan, but its purpose is to prevent one from violating an Isur Torah, thus the Torah dimensions of the Amah are to be applied, unlike the case of Techumin which has no origin in the Torah.

All the best,

Y. Landy

Hello again.

Yes this true, but this is an Asmachta. The Gemara on 36a considers Techumin something which does not have an origin in the Torah.

Kol tuv.

Y. Landy

The Gemara states in numerous places that Techumin are mid'Rabanan (except for the opinion of R' Akiva). See Sotah 27b and 30b.

Kol tuv.

Y. Landy