Chullin 91 - The Fight Between Jacob and Angel
The prohibition of eating the sciatic sinew applies to the sinew of the right thigh and of the left thigh, but Rabbi Yehudah says that it applies to only one thigh, and logic dictates that it should be the right one. Is this the logic of the Torah or of the Sages? In other words, is Rabbi Yehudah certain that the Torah prohibited only the right sinew, or is he uncertain which one is prohibited, and so both are prohibited out of doubt?
Consider the following rule: if one ate a portion of the right sinew and of the left one, then according to the Sages he incurs double punishment, eighty lashes, but Rabbi Yehudah gives him only one punishment. Now if Rabbi Yehudah is in doubt about which sinew it is, then the person eating it can only be given a doubtful warning, which is no warning at all! Must be then that Rabbi Yehudah is certain that only the right sinew is prohibited. Why the right one?
One explanation is that the angel fighting with Jacob embraced him with his right hand and extended it to Jacob's right haunch and dislocated it. Another one - Jacob thought it was a non-Jew and positioned him to his right, to better protect himself. Yet another explanation, the angel looked like a Sage, and Jacob position himself to the left of the Sage, to show respect.
Art: Luca Giordano - Jacob Wrestling With The Angel