Reference for Chullin 42:10

רבי אלעזר ברבי שמעון אומר

But then it should follow, should it not, that as in the former case one must nip through only one organ without severing the other,<span class="x" onmousemove="('comment',' For in connection with the sin-offering of a bird the Torah adds: And he shall not divide it asunder (Lev. I, 17) . Therefore the priest is not allowed to nip off any more than is necessary to render the bird valid i.e., one organ.');">⁷</span>

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