Because Mr. Mertle asked the cops how long he had to keep The Beast chained up like a slave, they said until forever.

11 seconds sound clip from the The Sandlot (1993) movie soundboard.

You can hear this line at 00:31:20 in the Blu-ray version of the movie.

Quote context

[...]

- Some people say they all got away. But we all know what really happened. The Beast ate them. He ate them bone and all.

- The Beast was too good at his guard dog job, so the police said he had to be retired.

- My grandpa, Squidman Palledorous, was police chiefback then.

- He ordered Mr. Mertle to turn his backyard into a fortress and chain up The Beast and put him under the house where he could never get out to eat children and stuff.

- And that's where he's been for 20 years. And that's where he'll be for the rest of his life.

- Because Mr. Mertle asked the cops how long he had to keep The Beast chained up like a slave, they said until forever.

- Forever. Forever. Forever. Forever. Forever.

- And so, The Beast sits there under that lean-to, dreaming of the time when he can break the chain and get out, dreaming of the time he can chase and kill again.

- See, man? That's why you can't go over there. Nobody ever has. Nobody ever will.

- One kid did, but nobody ever seen him again.

[...]