Musar for Shabbat 110:19

As long as the angel's prediction about G–d changing Jacob's name had not been fulfilled, Jacob still bore the marks of his nocturnal encounter with Samael on his body. Dinah's rape was the visible effect of the contact with impurity during the encounter in which Jacob's thigh joint was injured. One of his offspring, Dinah, became infected with טומאת מגע, impurity contracted due to contact with something impure, as a direct consequence of her father's physical contact with something impure. The Torah (34,2) describes the rapist as שכם בן חמור החוי. The word החוי is an allusion to the original serpent which is called חויא in Aramaic. We have explained earlier that this נחש, i.e. its power, is active within the ירך, reproductive organs of man, and that this is the connection with the prohibition of the גיד הנשה. Through Dinah's experience, and the incident with Reuben in Bilhah's tent described later in 35,22 (although our sages view Reuben's deed as symbolical rather than actual, Shabbat 55b), any lingering vestige of the serpent's pollution was drained from Jacob, and after that his "bed" could be described as totally pure, or שלימה, in the parlance of our sages. It was at this point that G–d Himself bestowed the name ישראל on Jacob and blessed him.