Meta. The rod represents spiritual power. Men have always considered a rod to be a symbol of power. The wizard waves a wand and the king carries a scepter to show his power. The staff or club is probably man's earliest tool. Through the ages it has assisted him inhis rise to mastery.
In the Bible the rod also represents life. In this connection note that Aaron's rod burst into bloom and also turned into a serpent (an Oriental symbol of life). Aaron symbolizes the executive function of divine law. This power expressed itself through his rod. So the rod may rightly be considered a symbol of the power of divine life.