Jay Z performed "Forever Young" with Justin Timberlake during his "Legends Of The Summer" concert performance at the Yankee Stadium and dedicated the song to Trayvon Martin. 

Jigga told the audience to put their cellphones in the air to honor Trayvon. 

"Everybody put a cell phone and light it up ... let's light the sky for Trayvon Martin tonight in here."

BONUS: Beyonce and Hov attend Trayvon Martin march in Manhattan.