Reference for Pesachim 166:7

ואלא תפשוט דספוקי מספקא ליה לר' יהודה דאי מיפשיט פשיטא ליה ההיא דהיתירא ניכליה ודאיסורא נישדייה למה ליה שריפה

But if you say that they are not flesh, why do they require burning? - Said R'Hisda: This [teaching] arises only in respect of the thigh sinew, and in accordance with R'Judah. For it was taught, R'Judah said: [The prohibition of the thigh sinew] is operative only in respect of one, and reason determines, that of the right [thigh].<span class="x" onmousemove="('comment',' V. Gen. XXXII, 33. Thus actually one of the thigh sinews is permitted, though we do not know which; this one therefore is really nothar and must be burnt.');">⁶</span>

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