Reference for Bekhorot 6:21

אי משום שינוי אפילו שתיהן גדולות שתיהן קטנות נמי

The reason is because it is a sarua'.<span class="x" onmousemove="('comment',' An animal whose one limb is larger than the other is called a sarua'. Therefore were it not stated in the House of Study that a change in the offspring e.g., where its wool resembles that of a goat, renders it blemished, I should not have been in a position to infer this from the Mishnah, as sarua' is a permanent blemish explicitly mentioned in the Scripture.');">¹⁵</span>

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