If I don't make it back, you're the only hope for the Alliance.
2 seconds sound clip from the Star Wars: Episode VI - Return of the Jedi movie soundboard.
You can hear this line at 01:19:43.762 in the Blu-ray version of the movie.
Quote context
[...]
- Luke, tell me, what's troubling you?
- Vader is here. Now. On this moon.
- I felt his presence. He's come for me. He can feel when I'm near.
- That's why I have to go. As long as I stay, I'm endangering the group and our mission here.
- Why?
- There's more. It won't be easy for you to hear it, but you must.
- If I don't make it back, you're the only hope for the Alliance.
- You have a power I don't understand and could never have.
- You're wrong, Leia. You have that power, too. In time, you'll learn to use it as I have.
- The Force is strong in my family. My father has it. I have it. And... my sister has it.
[...]