Reference for Bekhorot 6:19

(ויקרא כב, ד) איש איש מזרע אהרן דבעינן איש שוה בזרעו של אהרן אבל בהמה שתיהן גדולות שתיהן קטנות נמי לא הוי מומא

Must you not therefore admit that [the reason is] that we say since [the animal] is abnormal, it is regarded as a blemish?<span class="x" onmousemove="('comment',' What new thing consequently does R. Johanan tell us in his ruling that a change renders it blemished, since this may be inferred from the Mishnah?');">¹⁴</span>

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