Reference for Niddah 127:22

כיון דלמודה ועקרתיה בתרי זימני עקרה ליה קמ"ל

Now does not this<span class="x" onmousemove="('comment',' From which it is obvious that, since only three occurrences cause the abolition of the old, and the establishment of a new settled period, the first occurrence is not counted. ');">²⁰</span>

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