Measurements that go all the way back to Moses at Mount Sinai TB Eiruvin 4

Yesterday’s daf TB Shabbat 3b records a disagreement between Abaye and Rava concerning what is the length of an amah (אמה). Abaye says it can either be 5 tefakhim (טפחים)-handbreadth, or 6 tefakhim depending on the circumstances. He chooses which ever amah conforms to a more stringent position in order to err on the side of caution. Rava holds that an amah is always 6 tefakhim long; however, there is a little wiggle room. Sometimes a person uses an expansive handbreadth where the fingers are spread apart and sometimes he uses a compressed handbreadth.

Since we got onto the topic of measurements, today’s daf continues the discussion even though it has nothing to do with the alleyway (מבוי). Moses Maimonides in his introduction to the Torah sheba’al peh, the oral Torah, writes that it consists of five component parts. The first component are accepted for additional interpretations. An example would be the identification of the fruit of the hadar (literally beautiful) tree as the Etrog (Leviticus 23:40). The second component are those halakhot transmitted to Moses from Sinai which have no scriptural basis whatsoever. The third component are Rabbi Yishmael’s 13 principles by which the Torah is expounded. (They may be found on page 12 in Siddur Sim Shalom for Weekdays or any traditional prayer book before pesukai dezimra.) The fourth component are the gezairot (גזרות), a precautionary measures mostly in a restrictive sense enacted by the rabbis. The fifth and last component are the takanot (תקנות), ordinances, improvements, or measures for the public welfare enacted by the rabbis.

 Our Gemara TB Eiruvin 4 cites three examples of Rambam’s second component, halakhot transmitted to Moses from Sinai which have no scriptural basis whatsoever. “Since the Gemara discussed measurements, it proceeds to cite that which Rabbi Ḥiyya bar Ashi said that Rav said: The measures (שִׁיעוּרִין) relating to mitzvot in the Torah, and the halakhot governing interpositions (חֲצִיצִין) that invalidate ritual immersions, and the halakhot of partitions (מְחִיצִין) are all halakhot transmitted to Moses from Sinai. These halakhot have no basis in the Written Torah, but according to tradition they were orally transmitted by God to Moses together with the Written Torah.” (Sefaria.org translation) The Gemara will challenge whether these three laws have no scriptural basis by showing that they do! Depending on which halakhah is under investigation, the Gemara comes to the conclusion that at least some aspects of the laws were indeed transmitted to Moses from Sinai. If you’re interested, check them out for yourself starting with the measures at https://www.sefaria.org/Eruvin.4a.12?lang=bi&with=all&lang2=en.