Grounded, is a reference to a foundation, which refers to something that is permanently put in its place and is unmovable. The grounded staff, refers to the judgment of God, meaning with every stroke of punishment, that punishment is fixed upon the enemy, such that they cannot escape.
And taking off from the previous verse, the rod of Assyria, may inflict destruction, and to a certain extent is even allowed by God, as He allows Assyria to inflict punishment on disobedient people.
Jesus Christ controls history. Jesus Christ controls history in three ways.
First, He has direct control by means of His direct action. As God He created the universe, and angels, and every living thing, including humanity.
Second, Christ controls history through indirect control. By means of truth and Bible doctrine, and through the laws of divine establishment, humanity is guided by principles of law and order, due process, principles of free enterprise, and so forth.
Third, Jesus Christ controls history through permissive control. He allows the free will of man to function freely. And by this, people will choose either for good or for evil, which God allows that free choice, and thereby some people become aggressive, while others become passive. And to some extent, the laws of the jungle can rule throughout society. People can rise against people, nations can rise against nations. And by this God allows evil to fight evil, as it were. Needless to say, people suffer from the repercussions of their decisions.
But there is always a line drawn in the sand. Evil can go so far, yet no farther.
Israel had become evil, and therefore God allowed Assyria to punish Israel, by means of their invasion. Something that Israel brought on itself by being weak, by being unprepared, by choosing evil rather than truth, by choosing the world rather than God.
Anytime and every time, a person rejects God and turns to the resources of the world, then you can only expect that the evils of the world will turn against you.
But evil goes only so far. When God brings a halt to it, then we have here the strokes of God’s punishment, setting deep as a foundation, into those who would presume to take the law into their own hands.
And the result?
Evil is brought to a halt, defeated, and even overturned. The rod of Assyria is replaced by the rod of God.
The suffering and sorrows brought on by the attacks of evil, when evil is defeated, are replaced by the tambourines and music of deliverance and freedom.
And battling with the shaking or brandished arm, is a reference to only one person, namely Jesus Christ, who flexes the muscle of His will, and engages in a fight where the outcome is already determined.
And that fight of course, always results in a victory for Christ.