The killing of Jason would do you no good. Kill Jason and you kill yourself.
10 seconds sound clip from the Jason and the Argonauts (1963) movie soundboard.
You can hear this line at 00:07:12 in the Blu-ray version of the movie.
Quote context
[...]
- The child who has escaped you: Jason.
- Then why was I not told the whole prophecy?
- Why did Zeus drive me to kill this girl when the only one I needed to kill was Jason?
- Zeus cannot drive men to do what you have done.
- The killing of Jason would do you no good. Kill Jason and you kill yourself.
- Zeus, my godly husband, did you, for some reason order the profanation of my temple in Thessaly?
- I know that you've been insulted, my dear.
- But be content. The boy, Jason, has escaped. He will avenge you.
- How?
[...]