Verse three speaks of God, and then in verse four, Isaiah speaks of God’s people.
The noise of the tumult, is a description of a vast invading army, made up of multiple sources of people.
The Assyrian army back in Isaiah’s day, consisted of people that had been conquered by Assyria, from a vast number of nations and locations, and had been assimilated into the army to serve Assyria.
At the end of human history, during the tribulation, a similar invading army, that will be surrounding Israel and Jerusalem, will be made up of people from an even greater number of countries and locations. Likewise, it will be far more vast than any army of the past.
Seemingly indestructible and unstoppable, this huge world army, will be allowed to advance and destroy with impunity, until such time as God says enough. And Jesus Christ being God, will draw line, so to speak, that this invading army will be able to advance to, but will be stopped in their tracks and not allowed to go any further.
Jesus Christ controls history.
And those believers in Christ, who will be surrounded, and definitely outnumbered and outgunned, will be in the worst possible situation than anybody has ever been in, in all of human history.
And in the midst of the worst of all possible situations, this verse will be a source of comfort, in that those believers in Christ, knowing their doctrine, and in that future time of history, which we call the tribulation, they will know that this advancing, arrogant army, is going to be destroyed.
And it will not be destroyed by their hand, but by the hand of Christ.
And despite all of their resources and power and numbers, they will be sent running, and scrambling, and fleeing in total fear, as Jesus Christ will systematically pick them apart and destroy them, in short order.
Study [by instruction],
to show thyself approved [spiritually mature]
a workman [student]
that need not be ashamed [ignorant],
rightly dividing [learning, understanding, discerning]
the word of truth [Bible doctrine].
If you can dream and not make dreams your master,
If you can think and not let thoughts narrow your views,
If you can meet triumph with disaster equally,
If you can learn and see your full meaning and purpose in life,
Then you can believe in Christ, learn Bible doctrine, and grow far beyond the potential that God has prepared for you.