Eruvin 19B

שהן כעשר, דברי רבי מאיר. רבי יהודה אומר: כשלש עשרה אמה וכארבע עשרה אמה.

so that the total width of 6 oxen is approximately 10 cubits; this is the statement of R' Meir. R' Yehuda said the following, in accordance with his own opinion that the gap may be the size of two teams of 4 oxen each: The total width is approximately 13 cubits or approximately 14 cubits.

״כעשר״? הא עשר הויין! משום דבעי למיתנא סיפא ״כשלש עשרה״.

The Talmud asks: Why does the tanna of the baraita say: Approximately 10 cubits in R' Meir’s statement? Isn’t it exactly 10 cubits? The Talmud answers: Since he wanted to teach: Approximately 13, in the last clause, i.e., R' Yehuda’s statement, he therefore also taught: Approximately 10, in the first clause.

״כשלש עשרה״⁠ — טפי הויין? משום דבעי למתני ״כארבע עשרה״. ״וכארבע עשרה״⁠ — הא לא הויא? אמר רב פפא: יתירות על שלש עשרה, ואינן מגיעות לארבע עשרה.

The Talmud asks: But how could he say: Approximately 13, when it is more? The Talmud answers: Since he wanted to teach: Approximately 14, he therefore also teaches: Approximately 13. The Talmud continues this line of questioning: But they are not approximately 14, but rather are less. Rav Pappa said: It is a third of a cubit more than 13 cubits, and it does not reach 14 cubits.

אמר רב פפא: בבור שמונה דכולי עלמא לא פליגי דלא בעינן פשוטין.

Rav Pappa said: With regard to a water cistern whose own width is 8 cubits, everyone agrees, both R' Yehuda and R' Meir, that there is no need to position upright boards between the double posts. In such a case, the width of the enclosed area, which is the width of the cistern together with the space required for the cows, i.e., two cubits on each side, is 12 cubits. Since the width of each double post is 1 cubit, the gap between the double posts is 10 cubits, and a gap of this size is permitted even according to R' Meir.