Reference for Chullin 163:31

<big><strong>מתני׳</strong></big> שנים שלקחו פרה ובנה איזה שלקח ראשון ישחוט ראשון ואם קדם השני זכה:

A Tanna taught: If the second forestalled him he is sharp and gains an advantage; sharp in that he cannot now transgress the law, and gains an advantage in that he eats meat [to-day].<span class="x" onmousemove="('comment',' Whereas the other may not slaughter his animal until the next day.');">¹⁸</span>

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