Double entendre time! First level is that “foes” are enemies for Nas to defeat with his 9mm gun, but second level is that in a New York accent, “foes” sounds like “fours”, slang for a .44 Magnum handgun, used by Dirty Harry — a larger caliber handgun than Nas' 9 mm.

If Nas can defeat 4s with 9s, he is a skilled shooter.