Do not reveal yourself to Pelias, but build a ship and find a crew, and when you have this prize, then and only then... return and kill Pelias.
13 seconds sound clip from the Jason and the Argonauts (1963) movie soundboard.
You can hear this line at 00:13:14 in the Blu-ray version of the movie.
Quote context
[...]
- They would know that the gods have not abandoned them.
- My land would be rich and strong again, as it was before this tyrant, Pelias, murdered my father.
- First, search for this Golden Fleece.
- My companions are yours to command.
- Father, why do you let him live?
- If I destroy him, I destroy myself.
[...]