TT #217 · Parshas Shemini · Aliyah 7 · Passuk 37
Chabad.org — Vayikra Chapter 11 with Rashi
English: “When it falls”: the impurity applies only once the animal part has actually fallen; a detached limb or flesh still hanging by a hair does not have the full impurity of a carcass.
Chullin 127b.
E-Daf.com — Chullin 127b (Tsurras Hadaf)
Textual condition — The Chazal derives the stated rule from the wording and structure of the verse.
Impurity applies once the material has actually fallen.