The rod in biblical times was a two to four foot club used for defending the
sheep from predators and robbers.  It was worn in their belt and may resemble
a walking stick but was a weapon or tool to provide safety for the flock.

The staff was used to hold the sheep during shearing and for gentle correction
or re-directing. The hook at the top end of the staff was fit around the neck or
head of the sheep to re-route them. At the bottom end of the staff was a spoon-
shaped “shovel”. If the sheep wandered a bit from the herd, the shepherd
would scoop up a bit of mud or dirt and flick it at the sheep that had drifted to
catch its attention; hey the rest of the group is over here, there is safety within
the herd. The staff and rod also represented the head of household, the leader
and family representative.  Numbers 17:1-6

The staff represents God's Spirit. It indicates gentle guidance, whereas the rod
suggests sterner measures such as offense or defense—protection. God
leads, guides, by His Spirit.

In Egypt, the Pharaoh's were considered god. When they died, they had their
arms crossed. Right arm holding  the "rod" to ward off evil beings over the let
arm, holding the "staff", to keep their spirituality. The left arm is closest to the
heart, which they considered to hold their thoughts, knowledge and emotions.
Thus the reasoning for God "hardening" the Pharaoh's heart, making him