Yoda: Stopped they must be; on this all depends. Only a fully trained Jedi Knight, with the Force as his ally, will conquer Vader and his Emperor. If you end your training now - if you choose the quick and easy path as Vader did - you will become an agent of evil.
Obi-Wan: Patience.
Luke: And sacrifice Han and Leia?
Yoda: If you honor what they fight for? Yes.
Obi-Wan: If you choose to face Vader, you will do it alone. I cannot interfere.
Luke: I understand. R2? Fire up the converters.
Obi-Wan: Luke! Don't give in to hate. That leads to the Dark Side.
Yoda: Strong is Vader. Mind what you have learned. Save you it can.
Luke: I will. And I'll return, I promise.