Reference for Bekhorot 6:6

אלא מום קבוע מאי קא משמע לן דכיון דאישתני הוה ליה מומא

means that] it is [like a firstling with] a permanent blemish, on account of which it is slaughtered.<span class="x" onmousemove="('comment',' I.e., outside the Temple. And eaten like any other firstling which possesses a blemish. It is, however, not suitable for sacrifice on the altar. This was R. Johanan's novel ruling emanating also from the House of Study, i.e., that a change in the animal renders it blemished.');">⁵</span>

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