משנה: אָמַר לָהֶן רִבִּי עֲקִיבָה אֵי אַתֶּם מוֹדִין לִי בְּנוֹתֵן אֶת עֵירוּבוֹ עַל פִּי הַמְּעָרָה שֶׁאֵין לוֹ מִמְּקוֹם עֵירוּבוֹ אֶלָּא אַלְפַּיִם אַמָּה. אָמְרוּ לוֹ אֵימָתַי בִּזְמַן שֶׁאֵין בָּהּ דִּיוּרִין אֲבָל בִּזְמַן שֶׁיֵּשׁ בָּהּ דִּיוּרִין מְהַלֵּךְ אֶת כּוּלָּהּ וְחוּצָה לָהּ אַלְפַּיִם אַמַּה. נִמְצָא קַל בְּתוֹכָהּ מֵעַל גַּבָּהּ. וְלַמּוֹדֵד שֶׁאָמְרוּ נוֹתְנִין לוֹ אַלְפַּיִם אַמָּה שֶׁאֲפִילוּ סוֹף מִידָּתוֹ כָּלֶה בַמְּעֳרָה:
MISHNAH: Rebbi Aqiba told them, do you not agree with me about one who puts his eruv at the mouth of a cave that he only has 2’000 cubits from the place of his eruv? They told him, when is this? If there are no dwellers in it, but if it is inhabited he walks through all of it and outside 2’000 cubits. It turns out that the interior is easier than its top. But for one who measures about whom they talked one gives 2’000 cubits even if his measure reaches its limit inside the cave.