Reference for Niddah 43:11

{ויקרא טו } ממנו אמר רחמנא עד דנפיק מבשרו ולא בקיסם

while the Rabbis hold the opinion that the woman is clean and the interior of the uterus is also clean.<span class="x" onmousemove="('comment',' So that the blood remains clean even after it had passed through the uterus. ');">¹¹</span>

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