As Yaakov prepares to meet his brother Eisav for the first time in over twenty years, he encounters the spirit of Eisav, with whom he wrestles until daybreak. While Yaakov wins the fight, his hip is injured in the skirmish, which is why we are not permitted to eat similar sinews in animals (32:33). Why would Yaakov’s suffering an injury translate into our dietary laws and the restriction to eat that same tendon?
The Chafetz Chaim explains that the struggle between Yaakov and Eisav’s angel is an allegory for our everlasting and internal battles between good and evil. The injured tendon links the hip to the leg and is crucial to forward movement. The Torah memorializes the idea of turning a negative into a positive by converting the misfortune of Yaakov’s injury into the mitzvah of not eating that tendon. The practical lesson is to develop the attitude of turning setbacks into steps forward.