Reference for Bekhorot 51:36

ואי רבנן אידי ואידי מיסר אסרי

You can hardly say where he slaughtered [the firstling], for both Akabya and the Rabbis in both instances<span class="x" onmousemove="('comment',' Both where it is on a level with the rest of the wool and where it is not.');">¹⁶</span>

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