For over a thousand generations, the Jedi knights were the guardians of peace and justice in the old Republic, before the dark times, before the Empire.

Obi Wan Kenobi (Alec Guinness)

14 seconds sound clip from the Star Wars: Episode IV - A New Hope (1977) movie soundboard.

You can hear this line at 00:33:55 in the Blu-ray version of the movie.

Quote context

[...]

- Your father wanted you to have this when you were old enough, but your uncle wouldn't allow it.

- He feared you might follow old Obi-Wan on some damn-fool idealistic crusade like your father did.

- Sir, if you'll not be needing me, I'll close down for a while. Sure. Go ahead.

- What is it?

- It's your father's lightsaber.

- This is the weapon of a Jedi knight. Not as clumsy or random as a blaster. An elegant weapon for a more civilized age.

- For over a thousand generations, the Jedi knights were the guardians of peace and justice in the old Republic, before the dark times, before the Empire.

- How did my father die?

- A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi knights.

- He betrayed and murdered your father.

- Now the Jedi are all but extinct.

[...]