Question: Why does the injury Yaakov incurs when wresting with the angel translate into a prohibition against eating the Gid Ha-Nasheh (sciatic nerve) of an animal? What do the animals have to do with Yaakov's experience?
Answer: This question is not specific to this halachah but is relevant to many halachot. For example, when a person becomes impure, his purification is affected by the sprinkling of the ashes of the red heifer. The unsolved murder of a wayfarer is atoned for by a decapitated calf. A goat is sent to Azazel as part of the atonement process on Yom Kippur for the sins of the Jewish People. It is evident that there is a connection between human existence and the animal kingdom. This is because the whole of existence is a single organism referred to in Hebrew as the "Datzcham" Unit - an acrostic standing for the four realms of existence: a. "Domem" – inanimate elements. b. "Tzome'ach" – vegetation. c. "Chai" – the animals. d. "Medaber" – the speaking being, i.e. humans (See Orot Ha-Kodesh 2, p. 361). All levels are interrelated and connected through hidden pathways. We and the animals are connected. This was very obvious in Noach's Ark where the whole remnant of the animal world was dependent on Noach. Therefore, an improvement in one part of this united whole, such as in the animal kingdom, can heal and improve another part of the organism, namely, man. This is just like a human being who takes a tablet through part of his body and yet is healed an in entirely different part, because the same vitality flows through all of the limbs and thus unites them. A frailty in Yaakov's thigh thus can be reflected in the prohibition to eat a certain limb in an animal.