עַל־כֵּ֡ן לֹֽא־יֹאכְל֨וּ בְנֵֽי־יִשְׂרָאֵ֜ל אֶת־גִּ֣יד הַנָּשֶׁ֗ה אֲשֶׁר֙ עַל־כַּ֣ף הַיָּרֵ֔ךְ עַ֖ד הַיּ֣וֹם הַזֶּ֑ה כִּ֤י נָגַע֙ בְּכַף־יֶ֣רֶךְ יַעֲקֹ֔ב בְּגִ֖יד הַנָּשֶֽׁה׃
Therefore the children of Yisrael do not eat the sciatic nerve that is on the hollow of the thigh, to this day, because he touched the hollow of Yaakov’s thigh on the sciatic nerve.
Torah Temimah points to Pesachim 22a.
שולח אדם ירך לעובד כוכבים וגיד הנשה בתוכו, מפני שמקומו ניכר.
A person may send a thigh to a non-Jew with the sciatic nerve inside it, because its place is recognizable.
Practical permission to transfer a thigh containing the gid when the location remains visible.
Derash on practical application of the prohibition (Bavli).
One may send a thigh containing the sciatic nerve to a non-Jew when the place of the nerve is still identifiable.