In a well-known comedy routine, Bill Cosby reenacts Hashem instructing Noah to build the ark. Hashem instructs Noah to build the ark 300 cubits (amot) long, 50 cubits wide and 30 cubits high. At this point, Cosby portrays an incredulous Noah asking God, “What’s a cubit?” Bill Cosby likely did not realize it, but he raised an issue that is vigorously debated among poskim regarding which a significant difference exists between Sephardic and Ashkenazic traditions. This has important ramifications for building community eruvin. Eruv creators should bear the Sephardic standard in mind to ensure that the eruv satisfies Sephardic as well as Ashkenazic customs. This has specific application in regard to a recurring issue in most eruvin, gaps of up to 10 amot. The question becomes, as Bill Cosby said, “What’s a cubit (amah),” how much of a gap in terms of feet and inches may be tolerated.

Gaps of 10 Amot

Unlike the making of an eruv in the Jewish state where we are at home and government authorities are supportive, outside of Eretz Yisrael, especially in smaller Jewish communities, eruvin must be made in the least-intrusive manner as possible. Every effort should be made to use existing structures such as utility poles (especially those with a wire running on top of the pole), steep slopes and fences. In such situations, gaps will often exist when seeking to transfer from fences to poles to steep slopes, etc. The halacha tolerates a gap of up to 10 amot/cubits in such circumstances (see Mishnah Eruvin 1:1, Shulchan Aruch Orach Chaim 362:9 and Aruch Hashulchan O.H. 362:30 and 36 and 363:45).

Another measurement of major importance is the tefach (handbreadth). Walls are required to be at least ten tefachim high to be used as part of an eruv (Mishnah, Eruvin 1:9 and Shulchan Aruch O.C. 345:2). Thus, when constructing an eruv, one must specifically define two essential measurements—10 amot and 10 tefachim (there are 6 tefachim in an amah).

What’s a Cubit? What’s a Tefach?—Chazon Ish, Rav Moshe Feinstein and Rav Avraham Chaim Na’eh

Twentieth-century poskim intensely debate the equivalent of an amah and a tefach in contemporary terms. The very wide range of opinions on this matter is summarized in the Encyclopedia Talmudit (the entry “Amah”); the three primary opinions are that of the Chazon Ish, Rav Moshe Feinstein and Rav Avraham Chaim Na’eh. The Chazon Ish and Rav Na’eh were contemporaries living in Eretz Yisrael and engaged in vigorous debate about this topic from 5703/1943 until 5713/1953, the year in which both of these sages passed to the next world. Rav Moshe Feinstein issued his ruling on this issue in 1956 when he lived in the United States, independent of and without relating to the debate between the Chazon Ish and Rav Na’eh.

Their opinions are as follows: According to Rav Moshe Feinstein (Teshuvot Igrot Moshe O.H. 1:136), the amah is 21.25 inches (53.98 centimeters) and the tefach is 3.54 inches (9.00 centimeters). According to Rav Avraham Chaim Na’eh (in his famous work on the topic of shiurim, Shiurei Torah 3:25), the amah is 18.90 inches (48 centimeters) and the tefach is 3.15 inches (8 centimeters). According to the Chazon Ish (Chazon Ish to O.C. number 39), the amah is 24 inches (60.96 centimeters) and the tefach is 4 inches (10.16 centimeters).

Whose Opinion Is Followed—Sephardim and Ashkenazim

Ashkenazim and Sephardic poskim resolve this issue differently. In Eretz Yisrael (as reported in “The Laws of an Eruv” page 264 and Techumin 32:413), the custom among Ashkenazic authorities is to apply the stringencies resulting both from the Chazon Ish and Rav Avraham Chaim Na’eh’s opinion. Thus, they will require a fence to be 40 inches high but would not permit a gap greater than 15 feet and 9 inches. In the United States, both Rav Herschel Schachter and Rav Mordechai Willig follow Rav Moshe’s ruling in Teshuvot Igrot Moshe and they require a fence to be 36 inches high and permit a gap of up to 17 feet and 8 1/2 inches. “The Laws of an Eruv” (p.264) reports that “many poskim” in the United States adopt a similar approach.

Sephardim, however, follow the opinion of Rav Avraham Chaim Na’eh (Rav Avraham HaDa’yah, cited by Rav Avraham Chaim Na’eh in the introduction to his work “Shiur Mikveh” and “Yalkut Yosef” in many places, including O.C. 550 where he rules that it is sufficient for hadasim and aravot to be 3 tefachim long, according to the size of Rav Avraham Chaim Na’eh).

Rabbi Haim Jachter is spiritual leader of Congregation

Shaarei Orah, the Sephardic Congregation of Teaneck.

By Rabbi Haim Jachter