Grammar, Usage / Citing references not used in main paper [4]

Need help citing source! (MLA) in a research paper on Warren Buffett

I'm writing a research paper on Warren Buffett. In the beginning of my essay I started it off with this quote by Warren Buffett himself.

"If your're in the luckiest one percent of humanity, you owe it to the rest of humanity to think about the other 99 percent"

Ok, so basically my question is, when you normally site something you put ( ) right before the period and whatever is in the parentheses should match up to the first word in your works cited.

However, how do I cite something that's spoken by Buffett himself? The quote can be found on many different websites. Help please! thanks!!