Reference for Chullin 7:15

ליחוש דלמא האי הוא דהוה שחיט שפיר

But perhaps the Cuthean had made a sign on the bird [by which he recognized it]? - R'Merharsheya said: It is a case where [the Israelite] has crushed the bird.<span class="x" onmousemove="('comment',' Thus obliterating any distinguishing sign that may have been on it.');">⁶</span>

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