Saturday, September 26, 2020

What’s a cubit? (Amah) Eruvin 48

We’ve been studying the laws of Shabbat for about 6 months now making our way through massekhet Shabbat and 47 dappim in massekhet Eruvin. An assumed premise underpinning our study is that a person may not walk in a public domain רשות הרבים more than four amot, cubits. Finally in today’s daf TB Eruvin 48 we learn the source of this law. “The Gemara inquires about the basis of this law: These four cubits within which a person is always permitted to walk on Shabbat, where are they written in the Torah? 

“The Gemara answers: As it was taught in a baraita: The verse “Remain every man in his place; let no man go out of his place on the seventh day” (Exodus 16:29), means one must restrict his movement to an area equal to his place. And how much is the area of his place? A person’s body typically measures three cubits, and an additional cubit is needed in order to allow him to spread out his hands and feet, this is the statement of Rabbi Meir. Rabbi Yehuda says: A person’s body measures three cubits, and an additional cubit is needed in order to allow him to pick up an object from under his feet and place it under his head, meaning, to give him room to maneuver.” (Sefaria.org translation)

The Gemara asks what is the practical difference between Rabbi Meir and Rabbi Yehuda? “The  The Gemara answers: There is a practical difference between them in that Rabbi Yehuda provides him with exactly four cubits but no more; whereas Rabbi Meir maintains that we do not restrict him in this manner, but rather he is provided with expansive cubits, i.e., enough room to spread out his hands and feet, which measures slightly more than four cubits.” (Sefaria.org translation)

How long is an amah? The Gemara goes back and forth whether we use exact measurements or relative measurements (the size of an amah is the length from the elbow to the tip his middle finger of an average person). Finally “When Rav Mesharshiya’s son came before Rav Pappa, the latter said to him: Were we to be so precise, we would not be able to learn anything at all, as we would be too busy answering such questions.” (Sefaria.org translation)

On Rosh Hashana one of my sons asked me how long is an amah? The range of values of the length of the amah given in various sources gives the minimum as 48 cm = 1.57 ft = 0.52 yd and the maximum as 64 cm = 2.1 ft = 0.7 yd . “Sh”t Igrot Moshe O”C 1:136. writes that the Amah is 21.25 inches and one can be strict to hold that it is 23 inches. Similarly, the Aruch Hashulchan YD 286:21 writes that 4 amot is one Russian sazhen which is the equivalent of 7 feet =meaning that the amah is 21 inches. Dr. Gideon Freedman in Kol Bramah v. 4 p. 229 proves that the Aruch Hashulchan YD 201:3 and Mishna Brurah 358:7 both hold that the amah is 21 inches. The Aruch Hashulchan says that an amah is three quarters of a arshin and an arshin is 71.12 cm. The Mishna Brurah ties 53 russian arshins to 70.83 amot. Chazon Ish is reported to say that an amah is 24 in. (60.96 cm)” https://www.halachipedia.com/index.php?title=Reference_of_Measurements_in_Halacha#Amah.2C_Tefach.2C_Etzbah


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