Reference for Niddah 75:1

אפי' ימים הראויין לספירת סתירת זבה

even the days that are suitable for counting after the previous counting had been rendered void<span class="x" onmousemove="('comment',' I.e., for ever, since any seven days following a discharge that occurred within any seven days counted after a previous discharge are suitable for counting. ');">¹</span>

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