Reference for Bekhorot 42:39

<big><strong>מתני׳</strong></big> רבי אליעזר בן יעקב אומר

<big><b>MISHNAH: </b></big>R'ELIEZER B. JACOB SAYS: IF A LARGE DOMESTIC ANIMAL HAS DISCHARGED A CLOT OF BLOOD, IT [THE CLOT] SHALL BE BURIED,<span class="x" onmousemove="('comment',' For it is forbidden to use it profitably in case it was a male embryo which was mashed and was sanctified as a firstling.');">³⁰</span>

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