A nation is named after an inconclusive fight in the dark, with an opponent the text refuses to identify. Jacob is alone, having sent his family across the river ahead of him, and a man wrestles with him until dawn; unable to win, the other dislocates his hip and asks to be released before daybreak. Jacob demands a blessing and is given a new name, Yisrael, glossed in the verse as one who has struggled with God and with men and prevailed. He then names the place Peniel, saying he has seen God face to face and lived. The rabbis identified the opponent as Esau's guardian angel; Hasidic readings make it Jacob's own self; the plain text leaves it open. What is not open is the cost: he limps away from it, and Jews to this day do not eat the sciatic nerve of an animal, which makes the hindquarters of a kosher animal difficult enough to prepare that most communities outside Israel simply do not sell them.