Reference for Niddah 42:42

והא"ר יוחנן משום רבי שמעון בן יוחי

— Read: For R. Eliezer ruled, 'In her flesh' implies: But not [where the blood was] within a sac or within any shapeless abortion). But the Sages ruled: This is not menstrual blood but the blood of a shapeless object.<span class="x" onmousemove="('comment',' The woman is consequently clean. ');">³⁵</span>

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