If you're interested, that's the man that sold me the roan horse.
5 seconds sound clip from the The Westerner (1940) movie soundboard.
You can hear this line at 00:23:55 in the DVD version of the movie.
Quote context
[...]
- You're loco, brother. I don't owe you nothing.
- If you're interested, that's the man that sold me the roan horse.
- Then, he's the man that stole...
- Fined 80 dollars for disorderly conduct, and 4 dollars and 6 bits for carrying concealed weapons.
- Now, you men get some rope and string him up.
[...]