But what about the Rambam? How does he explain Abraham disinheriting Keturah’s children?
Let us delve more into the Rambam’s position. The Gemara (Chullin 100b) states: “[The prohibition of gid hanasheh, the sciatic nerve] applies to clean [kosher] animals but not to unclean [treif] animals. R. Judah says that it applies even to unclean animals. He argues that thegid hanasheh was not prohibited from the time of the sons of Jacob since unclean animals were still permitted to them at that time. They [the Sages] responded: This law was ordained at Sinai but was written in its proper place.”
The Gemara (infra 101b) explains the Sages’ argument: “They said to R. Judah, Does the Torah state, ‘Therefore the children of Jacob shall not eat [the sciatic nerve]?’ Surely not. It states, ‘Therefore the children of Israel shall not eat the sciatic nerve.’ And they were not referred to as B’nei Yisrael – children of Israel – until [Moses received the law at] Sinai. Therefore, we must say that the law of gid hanasheh was given at Sinai but was written [by Moses – see Rashi] in its present place to indicate why it became prohibited to them. Now Raba raised an objection to this argument: The Torah states, ‘Vayis’u b’nei Yisrael at Yaakov avihem – and the sons of Israel carried Jacob their father.’ [We thus see that they were referred to as B’nei Yisrael even before Maamad Har Sinai.] The Gemara answers: That was after the incident [of Jacob wrestling with the angel]. R. Aha b. Raba said to R. Ashi, ‘Then it should have been prohibited from that time onwards [from when they carried their father to Egypt].’ R. Ashi replied, ‘Was the Torah given at various times? That time was neither the time of the incident nor the time of the giving of the law.’”
The Rambam (in his Pirush haMishnayot commentary) explains this mishnah as follows: “Now pay close attention to the important rule in this mishnah [inherent in its] statement that the [sciatic nerve] was forbidden at Sinai: All that we distance ourselves from and all that we do is only because of G-d’s command through Moses, of blessed memory – not because G-d spoke to the prophets before him [such as the patriarchs]. For example, a limb torn from a living animal is not prohibited to us because it was prohibited to Noah; rather, it is because Moses [was so commanded by G-d] at Sinai.
“Similarly, we do not circumcise ourselves because Abraham, of blessed memory, circumcised himself and the members of his household; rather, we do so because Moses commanded us to circumcise in the manner that Abraham circumcised. The same applies to the sciatic nerve. We do not follow the prohibition to the patriarch Jacob. Rather, we forbid it because we were so commanded by our teacher Moses. This is what our Sages state (Makkot 23b): All 613 commandments were said to Moses at Sinai, and all of these [even those that appear in the Torah before Maamad Har Sinai] are included in those commandments.”
In light of this statement, I humbly offer the following as the Rambam’s reason for including not only the children of Keturah in the command of circumcision, but their progeny as well. Since a second verse – Genesis 17:14: “…et briti heifer” – is needed to include them, perhaps (exactly the opposite of how I see Rashi explaining the Gemara) it is there to stress that regarding this single solitary commandment, they are obligated like the Jewish people – i.e., the second verse imposes an obligation for all their generations.
(To be continued)