Reference for Niddah 141:22

אלא טעמא דב"ש כדתניא

CONVEYS UNCLEANNESS AS A BLOODSTAIN<span class="x" onmousemove="('comment',' Of a menstrual discharge. As the blood of a corpse it could convey no uncleanness unless it consisted of no less a quantity than a quarter of a log. ');">²⁰</span>

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