על כן לא יאכלו בני ישראל את גיד הנשה
בראשית לב – לג
What
Do not eat the Gid Ha`Nashe, the sciatic nerve of an animal
When
Anytime
Who
Everyone
Where
Anywhere
Additional details
In Chullin Perek 7
Why
So we remember that as Hashem saved Yaakov Avinu from Esav's Malach, so too Hashem will save us from destruction and redeem us.
If one eats it
Bais Din gives them Malkos