I think this is it...
Pull your pants up guys... Nobody wants to see your undies.
(taken from an interview with MTV)
But while he does not favor legal prohibitions on low-riders, he said "brothers should pull up their pants."
"Having said that," he added, "brothers should pull up their pants. You are walking by your mother, your grandmother, your underwear is showing. What's wrong with that? Come on. There are some issues that we face, that you don't have to pass a law, but that doesn't mean folks can't have some sense and some respect for other people and, you know, some people might not want to see your underwear -- I'm one of them."