Don't Stop Believin'

(25) And Jacob was left alone; and there wrestled a man with him until the breaking of the day. (26) And when he saw that he prevailed not against him, he touched the hollow of his thigh; and the hollow of Jacob’s thigh was strained, as he wrestled with him. (27) And he said: ‘Let me go, for the day breaketh.’ And he said: ‘I will not let thee go, except thou bless me.’ (28) And he said unto him: ‘What is thy name?’ And be said: ‘Jacob.’ (29) And he said: ‘Thy name shall be called no more Jacob, but Israel; for thou hast striven with God and with men, and hast prevailed.’...

(33) Therefore the children of Israel eat not the sinew of the thigh-vein which is upon the hollow of the thigh, unto this day; because he touched the hollow of Jacob’s thigh, even in the sinew of the thigh-vein.

...This event is entirely a hint for the coming generations, there will be a time in history of Jacob’s descendants that Esav will try to overcome them and Esav will almost exterminate them...This is a symbolic message for the Jewish people that no matter what horrible oppression comes their way, they will always survive intact, just as Jacob survived the fight with Esav's angel.

And it is this that has stood for our ancestors and for us, since it is not [only] one [person or nation] that has stood [against] us to destroy us, but rather in each generation, they stand [against] us to destroy us, but the Holy One, blessed be He, rescues us from their hand.

(2) Of the roots of this commandment: To serve as an indication to Israel that though they will suffer in the exile by the nations and the descendants of Esau, [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.