Reference for Chullin 148:44

מר זוטרא אמר

then it should follow, just as there the lamb must be a male, without blemish, of the first year,<span class="x" onmousemove="('comment',' Ibid. XII, 5. And just as a lamb which had been extracted from the ewe's womb is unfit for the paschal offering or any offering, it is likewise not fit for redeeming the firstling of an ass.');">²¹</span>

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