Eventually the pendulum swings
A pendulum is a weight suspended from a pivot so it can swing freely. Due to gravity and the various interactions of forces, a pendulum will always swing to and from its resting position (equilibrium). If left alone, the pendulum always comes back swinging.
In a similar fashion, Jay-Z came back swinging from his humble beginnings in the Marcy Projects. Now he’s one of the richest hip-hop artists around.
The idioms made to testify to this are countless: everything comes back to haunt you, karma is a bitch, what comes around goes around; however you want to put it, Jigga’s time is here.
He truly started from the bottom, now he’s here.
This line’s also a metaphor: Jay is a pendulum, always in rhythm and motion, and he’ll start swinging (throwing punches) when someone starts talking about his kid.
Could be referring to the pendulum blades that kings of old used to behead those that opposed them.
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