Reference for Bekhorot 6:13

כיון דאישתני הוה ליה מומא

but here the firstling has changed into a species [of animal] in which the sanctity of the firstling does exist,<span class="x" onmousemove="('comment',' And therefore this would be the novelty in the ruling of R. Johanan, that even in such an instance it is regarded as a blemish.');">⁹</span>

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