Reference for Chullin 259:20

מה ללקוח ויתום שכן נכנסין במינן לדיר להתעשר

ARE EXEMPT FROM THE LAW OF THE FIRSTLING, AND FROM THESE DUES, AND THEY MAY NOT, LIKE UNCONSECRATED ANIMALS, BE SHORN OR PUT TO WORK, AND [EVEN] AFTER THEY HAVE BEEN REDEEMED THEIR YOUNG<span class="x" onmousemove="('comment',' It is assumed that the animal became pregnant before it was redeemed and brought forth its young after redemption; v. Bek. 14a.');">¹⁶</span>

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