Halakhah sa Genesis 32:33: Sefer HaChinukh, Mishneh Torah, Forbidden Foods, Gray Matter II & Mishneh Torah, Negative Mitzvot

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.

Spannader, unbekanntes Fleisch, Verbot der Nutznießung
Das Verbot des Genusses der Spannader findet bei reinem Vieh und Tiere statt, selbst wenn sie als Gefallenes oder Zerrissenes betrachtet werden; ebenso beim Fetus, und bei Tieren, die zum Opfer geheiligt wurden, wobei es sich gleich bleibt, ob es Opfer sind, die gegessen werden können oder nicht, ebenfalls bleibt es sich gleich, ob es die Spannader des rechten oder linken Schenkels ist; — nach der Schrift aber sind nur diejenigen Adern verboten, die auf dem Becken liegen, denn es heißt (Gen. 32:33): »Die auf dem Kopfe des Hüftknochens«; das Übrige von der Spannader, so über, wie unter dem Becken, wie auch das Fett, das sich um diese Ader befindet, ist nur laut Vorschrift der Rabbinen verboten. Übrigens gibt es zwei Spannadern, das Verbot der Schrift nun bezieht sich nur auf die innere, die dem Knochen naheliegt, das Verbot der äußern rührt ganz von den Schriftgelehrten her.

Rav J. David Bleich and Rav Moshe Shternbuch (Moadim Uzmanim 5:351) add that we similarly do not know how to resolve halachic disputes concerning the Temple service, due to the lack of a tradition on how to conduct various rituals.¹⁹Rav Shternbuch notes that without the ability to resolve these disputes, offering korbanot risks violating many prohibitions entailing the severe punishment of kareit. He suggests, however, that the desire to explore the possibility of offering korbanot in the pre-Messianic era pleases God, as it shows that His people sincerely desire to fulfill His mitzvot. Rav Shternbuch uses this approach to explain the phenomenon of an extensive literature exploring the viability of offering korbanot today. Only the Mashiach’s arrival will enable us to renew this tradition.²⁰See Tosafot (Pesachim 114b s.v. Echad Zeicher), who write that Moshe and Aharon will instruct us in the rituals of the korbanot for the Third Temple. For example, Rav Bleich (Contemporary Halakhic Problems 1:266-267), citing Rav Meir Auerbach (Halevanon 1:8 p. 54), notes a disagreement between the Rambam and the Ra’avad (Hilchot Korban Pesach 10:11) about whether the gid hanasheh (sciatic nerve)²¹The Torah prohibits eating this nerve (Bereishit 32:33). of the sheep is roasted along with the rest of the Korban Pesach. One cannot simply be strict and follow both opinions, since if one were to follow the Ra’avad and remove the nerve, the animal would no longer be “whole” according to the Rambam, thus invalidating it. On the other hand, leaving the gid hanasheh in the animal invalidates it according to the Ra’avad. Rav Shternbuch lists a host of other gray issues regarding the priestly garments, such as how to design the avnet (belt), ketonet (tunic), and migba’at (hat) of the ordinary Kohein. We do not even know how to identify the color argaman, used in the making of the priestly garments.