זוהר בראשית — דף קעא ע”א

The Zohar explains that Moses looked through the luminous mirror, while the other prophets were weakened, except Obadiah the convert, who came from Esau’s side. The appointed one took the strength of the thigh, and the pillars of the Torah were weakened as well; when no one supports the Torah, the wicked kingdom grows stronger. The serpent must go “on your belly”; supports are given to it when Israel does not support the Torah. The appointed one acted cunningly toward Jacob: if “the voice of Jacob” ceases, then “the hands are the hands of Esau”; therefore he touched his thigh. At dawn Jacob prevailed over him and received a blessing from him, becoming Israel. The sinew was not broken, which is why it is not eaten.