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!
The Divine Law has preserved for all time the memory of this incident by the prohibition of the Gid Hanoshe. This could certainly not serve the purpose of informing Yaakov's descendants of the fact that their forefather limped as a result of a "wrestling match". This prohibition rather serves to immortalize and revive ever anew eternal truths which are of basic importance for the proud destiny of our people. "the vein of weakness" (related to ----, the creditor on whom the debtor depends; also ---, women). By tearing it loose the enemy broke Yaakov's strength to plant his feet firmly on the ground. Thus the expression "vein of weakness" is not so much an anatomical term as it is an historical reference. This vein must not be eaten by Yaakov's sons. Whenever they sit down to eat, the Book of Life is to confront them with this great admonition: During the nocturnal struggle Esau can neither conquer nor crush Yaakov, but he is able to tear the vein from its socket and impair his firm step on earth. Yaakov goes through history, limping. Yet this physical weakness is needed to open Esau's eyes to perceive the real forces that alone are responsible for Yaakov's invincibility. In joyful devotion Yaakov's nation is to renounce its claim to this vein, realizing that its continued existence through the course of history depends neither on this vein nor on its loss. if Yaakov falls, it is not because his material potency does not measure up to Esau's; if he falls, it will be because he failed to cultivate the Divine protection. When Israel stands firm it is not because of its physical and material strength - it stands, because G'd carries it on the eagle's wings of His Omnipotence.
