Reference for Eruvin 27:13

והאמר ר' אילעאי אמר רב רחבה ארבעה אע"פ שאינה בריאה רחבה ארבעה שאני:

provided only that the higher one was not higher than twenty cubits<span class="x" onmousemove="('comment',' From the ground (cf. Mishnah supra 2a ab init.) .');">¹⁴</span> and the lower one [was not] lower than ten cubits.<span class="x" onmousemove="('comment',' From the ground (cf. Mishnah supra 2a ab init.) .');">¹⁴</span>

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