To "ride for" someone in the literal sense means to ride in the car as the shooter during a drive by shooting. In the figurative sense, it means to support and stand by a friend until the very end, through any obstacle.
In Lyrics: Lil Wayne's "Sky's The Limit / Ride For My Niggas": "you know that ima ride for my motherfuckin niggas, most likely ima die with my finger on the trigger, don't worry bout mine, ima grind til i get it, and tellin all my niggas that the sky is the limit."
In a sentence: That fool was talking slick about my brother, so I had to stomp him out. Everybody knows I ride for my niggas.