Reference for Avodah Zarah 99:6

אמר רבא לא קשיא כאן בתפיסה אחת כאן בשתי תפיסות וה"ד דאיכא גובהה ביני וביני

Rava explained: There is no contradiction; here they were within one reach, and there within two reaches. What is this case? There is a mound between [the stones] and the Mercurius.

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