שֶׁלֹּא לֶאֱכֹל גִּיד הַנָּשֶׁה – וַיִּשְׁלַח יַעֲקֹב יֵשׁ בָּהּ מִצְוַת לֹא תַעֲשֶׂה אַחַת, וְהִיא אַזְהָרַת גִּיד הַנָּשֶׁה, שֶׁנֶּאֱמַר: (בראשית לב:לג) עַל כֵּן לֹא יֹאכְלוּ בְנֵי יִשְׂרָאֵל אֶת גִּיד הַנָּשֶׁה. וְהַאי לֹא יֹאכְלוּ לֹא נֶאֱמַר עַל דֶּרֶךְ סִפּוּר, כְּלוֹמַר מִפְּנֵי שֶׁאֵרַע דָּבָר זֶה בָּאָב, נִמְנָעִים הַבָּנִים מִלֶּאֱכֹל אוֹתוֹ הַגִּיד, אֶלָּא אַזְהָרַת הַשֵּׁם יִתְבָּרַךְ שֶׁלֹּא יֹאכְלוּהוּ. Not to eat the sciatic nerve: [Parashat] Vayishlach has one negative commandment, and it is the prohibition of [eating] the sciatic nerve; as it is stated (Genesis 32:33), “Therefore the Children of Israel shall not eat the sciatic nerve.” And this [phrase] “they shall not eat” is not to be taken as part of the story, to mean that because this event occurred to [our] forefather, [we, his] descendants refrain from eating that nerve. Rather, it is a warning (prohibition) of God that they shall not eat it.
מִשָּׁרְשֵׁי מִצְוָה זוֹ, כְּדֵי שֶׁתִּהְיֶה רֶמֶז לְיִשְׂרָאֵל, שֶׁאַף עַל פִּי שֶׁיִּסְבְּלוּ צָרוֹת רַבּוֹת בַּגָּלוּת מִיַּד הָעַמִּים וּמִיַּד בְּנֵי עֵשָׂו, יִהְיוּ בְּטוּחִים שֶׁלֹּא יֹאבְדוּ, אֶלָּא לְעוֹלָם יַעֲמֹד זַרְעָם וּשְׁמָם, וְיָבֹא לָהֶם גּוֹאֵל וְיִגְאָלֵם מִיַּד צָר. וּבְזָכְרָם תָּמִיד עִנְיָן זֶה עַל יַד הַמִּצְוָה שֶׁתִּהְיֶה לְזִכָּרוֹן, יַעַמְדוּ בֶּאֱמֻנָתָם וּבְצִדְקָתָם לְעוֹלָם. וְרֶמֶז זֶה הוּא לְפִי שֶׁאוֹתוֹ מַלְאָךְ שֶׁנִּלְחָם עִם יַעֲקֹב אָבִינוּ, שֶׁבָּא בַּקַּבָּלָה (בר"ר עח) שֶׁהָיָה שָׂרוֹ שֶׁל עֵשָׂו, רָצָה לְעָקְרוֹ לְיַעֲקֹב מִן הָעוֹלָם הוּא וְזַרְעוֹ וְלֹא יָכוֹל לוֹ, (שם לב כו) וְצִעֲרוֹ בִּנְגִיעַת הַיָּרֵךְ. וְכֵן זֶרַע עֵשָׂו מְצַעֵר לְזֶרַע יַעֲקֹב, וּלְבַסּוֹף תִּהְיֶה לָהֶם תְּשׁוּעָה מֵהֶם. וּכְמוֹ שֶׁמָּצִינוּ (שם שם לב) בָּאָב שֶׁזָּרְחָה לוֹ הַשֶּׁמֶשׁ לְרַפּאֹתוֹ וְנוֹשָׁע מִן הַצַּעַר, כֵּן יִזְרַח לוֹ הַשֶּׁמֶשׁ שֶׁל מָשִׁיחַ וִירַפְּאֵנוּ מִצַּעֲרֵנוּ וְיִגְאָלֵנוּ בִּמְהֵרָה בְּיָמֵינוּ, אָמֵן. It is from the roots of this commandment [that it is to serve as] a hint to Israel that though they will suffer many troubles in the exile by the hand of the nations and by the hand of the [descendants] of Esav (i.e. the Christians), [the Jews] should trust that they will not perish, but rather that their descendants and name will stand firm forever, and that their redeemer will come and redeem them from their oppressor. And in continually remembering this idea through the commandment that serves as a reminder, they will stand firm in their faith and righteousness forever. And this hint [stems from the fact that] that the angel who fought with Yaakov our forefather — who according to tradition (Bereshit Rabbah 78) was the guardian angel of Esav — wished to eliminate Yaakov from the world, he and his descendants; but he could not [get the better] of him, (Genesis 32:26) but anguished him in injuring his thigh. Likewise, Esav’s seed anguishes the seed of Yaakov; but in the end, [the latter] will be saved from them. As we find (Genesis 32:32) with respect to [our] forefather that the sun shone to heal him and he was saved from pain, so will the sun of the messiah shine and he will heal us from our pain and redeem us speedily in our days, amen!
דִּינֵי הַמִּצְוָה זוֹ מַהוּ הַגִּיד הָאָסוּר, וְהַחִטּוּט שֶׁאָנוּ חַיָּבִים לְחַטֵּט אַחֲרָיו, וּבְאֵי זוֹ בְּהֵמָה נוֹהֵג, וּמִי נֶאֱמָן עַל נִקּוּרוֹ וְיֶתֶר פְּרָטֶיהָ מְבֹאָרִים בְּפֶרֶק ז' מֵחֻלִּין (פט, ב) (י"ד סי' ס"ה). The laws of this commandment — which sinew is prohibited; the clearing out, that we are obligated to clear out [its area] after it; with regards to which beast it applies; who is trustworthy regarding its removal; and the rest of its details — are explained in the seventh chapter of Chullin. (See Tur, Yoreh Deah 65.)
וְנוֹהֶגֶת מִצְוָה זוֹ בְּכָל מָקוֹם וּבְכָל זְמַן, בִּזְכָרִים וּבִנְקֵבוֹת. וְהָעוֹבֵר עָלֶיהָ וְאָכַל גִּיד אֶחָד, אֲפִלּוּ הוּא פָּחוֹת מִכַּזַּיִת אוֹ שֶׁאָכַל כַּזַּיִת מִגִּיד הַנָּשֶׁה גָּדוֹל, לוֹקֶה. (עי' חולין צו, א) And [it] is practiced in every place and at all times by males and by females. And one who transgresses it and eats a [whole sciatic nerve], even if it is less than an olive’s worth — or eats a kazayit (the size of a large olive) from a large sciatic nerve — is lashed. (See Chullin 96a.)
מִכָּאן עַד סוֹף סֵפֶר בְּרֵאשִׁית אֵין בּוֹ מִצְוָה. נִשְׁלַם סֵפֶר בְּרֵאשִׁית. From here until the end of Genesis there are no commandments. The Book of Genesis is complete.