It is related in the Tanach that Amnon loved his sister Tamar greatly and desired her, wanting to have sex with her. In the end he raped her and after the rape it is written “Then Amnon hated her exceedingly, so that the hatred with which he hated her was greater than the love with which he had loved her” (II Samuel 13:15). The sages asked: What caused Amnon to hate Tamar after the rape? Answer: During the rape her pubic hair became entangled around his sexual organ and castrated him. The scholars asked: What fault is it of Tamar’s that her hair became entangled around his sexual organ? Answer [it is natural that topics passed down orally will be subject to distortions, and the scholars of the study hall would correct them to reconcile with what seemed to them reasonable]: It should read “entangled” instead of “became entangled.” Tamar herself tied her pubic hair around Amnon’s sexual organ and castrated him. The scholars continued to ask: It is a custom of Jewish women to shave their pubic hair, so how did Tamar have any pubic hair at all? Answer: Since Tamar was not Jewish on both side, only through her father (King David) while her mother was a gentile [David fell in love with a gentile captive and took her to wife, what is called by the sages “A beautiful woman [captive]”] she did not have the custom of shaving her pubic hair.
(Babylonian Talmud, Tractate Sanhedrin 21a)