Die is Cast

[Frank Abate]

This does originate with Julius Caesar, the Latin being "Alea iacta est".
When JC crossed the River Rubicon in northern Italy with his army, violating
a restriction placed on Roman generals, he said the phrase, meaning "There's
no going back", that he had taken the risk of provoking civil war by his
violation of the law.

I don't have access to sources now to give a date (about 48 BC) and cite, but
perhaps someone else?

Frank Abate