Genesis 32: 23 - 33
23 He took them and sent them across the stream, and likewise everything that he had.
24 And Jacob was left alone; and a man wrestled with him until the breaking of the day.
25 When the man saw that he did not prevail against Jacob, he touched the hollow of his thigh; and Jacob's thigh was put out of joint as he wrestled with him.
26 Then he said, "Let me go, for the day is breaking." But Jacob said, "I will not let you go, unless you bless me."
27 And he said to him, "What is your name?" And he said, "Jacob."
28 Then he said, "Your name shall no more be called Jacob, but Israel, for you have striven with God and with men, and have prevailed."
29 Then Jacob asked him, "Tell me, I pray, your name." But he said, "Why is it that you ask my name?" And there he blessed him.
30 So Jacob called the name of the place Peni'el, saying, "For I have seen God face to face, and yet my life is preserved."
31 The sun rose upon him as he passed Penu'el, limping because of his thigh.
32 Therefore to this day the Israelites do not eat the sinew of the hip which is upon the hollow of the thigh, because he touched the hollow of Jacob's thigh on the sinew of the hip.

EWTN