40-16 Building is the fourth track off Nas' 14th studio album, Magic.
In this song, Nas elaborated on how hateful/jealous people want to destroy anybody who successfully made it out their negative urban predicament, similar to how he opened up on this topic on his heartfelt song Moments from the KD2 album:
40-16 is probably a building in the 40 Side of Vernon in Queensbridge neighbourhood where Nas grew up.