Reference for Niddah 120:21

אבא תני מעשה בא לפני חכמים וטמאום ואת אמרת הלכה כרבי נחמיה

If it was found under the outer one,<span class="x" onmousemove="('comment',' A position which the inner one would never occupy, the tendency being to come up as close as possible to the mill. ');">²²</span>

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