Genesis 32:32

Therefore the children of Israel The Compiler adds this note, which explains the Israelite custom of abstaining from eating the muscle in an animal, corresponding to the muscle, or sinew, in the thigh of Jacob that was touched by God: it was regarded as sacred.

This tendon is commonly supposed to be the sciatic muscle, nervus ischiaticus, running from the thigh to the ankle. No mention of this practice of ritual abstinence occurs in the Levitical law; but it is referred to in the Talmud Tract Chullin, cap. vii.

he touched The subject to the verb is not expressed, out of motives of reverence.

"The nature of the lameness produced by injury to the sinew of the thigh socket is explained by the Arabic lexx., s.v. ḥârifat; the man can only walk on the tips of his toes" (!). Robertson Smith, Rel. Sem(380, n. 1).