Marty, I gave you explicit instructions not to come here, but to go directly back to 1985.

8 seconds sound clip from the Back to the Future Part III movie soundboard.

You can hear this line at 00:35:09.700 in the DVD version of the movie.

Quote context

[...]

- I done shot that horse!

- Well, that's your problem, Tannen.

- Wrong. That's yours.

- So from now on, you better be looking behind you when you walk. Because one day you're gonna get a bullet in your back.

(COWBOYS URGING HORSES)

- Doc!

- Marty, I gave you explicit instructions not to come here, but to go directly back to 1985.

- I know, Doc, but I had to come.

- But it's good to see you, Marty.

- You're gonna have to do something about those clothes. You walk around town dressed like that, you're liable to get shot.

- Or hanged.

- What idiot dressed you in that outfit?

- You did.

[...]