Reference for Chullin 258:25

ואי אין מיתה עושה ניפול ליטמא משום אבר מן המת

<big><b>GEMARA: </b></big>Whichever view R'Simeon takes [it is difficult]: If at death the limb is considered as already fallen off, then it should be unclean as a limb severed from the living body, and if at death it is not considered as already fallen off, then it should be unclean as a limb severed from a corpse! - R'Simeon refers to the law in general.<span class="x" onmousemove="('comment',' And he holds that a limb (entirely without flesh) severed from a corpse does not convey uncleanness!');">¹³</span>

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