Rabbi Chiya opens a discussion on the significance of the sinew of Jacob's thigh, which we can now identify as the sciatic nerve. Had the sinew not failed Jacob on the night he struggled with Esau's minister, Jacob would have prevailed over Esau's power completely, both on high and here below. Rabbi Shimon then explains that because the energy of Jacob's thigh was broken; the strength of the upholders of the Torah was diminished. As a result, none of the prophets, except Moses, was able to retain his faculties unimpaired when receiving divine messages. Thus, it is incumbent on the children of Yisrael to preserve the sinew of the thigh vein. The dark side controls the sciatic nerve in all creatures, including cows, so that none may be defiled by eating or benefiting from it in other ways. In addition, we learn, the children of Yisrael are responsible for preserving the power of the Torah by supporting those who toil in it.
The sciatic nerve affects the lower back and extends down through the thigh, which supports and upholds the body. The thigh corresponds to the students of a righteous sage who support their master, or to benefactors who financially assist those who engage in Torah study and the revelation of spiritual Light. When the dark side seeks to penetrate an individual, it will often attack supporting elements that are not as strong as the person himself. The Evil Inclination will strike first at our vulnerabilities and weaknesses. These verses fortify our defenses. In addition, we arouse great spiritual Light to strengthen those who support the righteous in their endeavor to reveal the Light of the Torah to all the world.