Isaiah 40 – …with His arm ruling for Him … What does that mean? What is that referring to?

Isa 40:10
Behold, the Lord GOD will come with might, With His arm ruling for Him. Behold, His reward is with Him, And His recompense before Him.

Isaiah now tells us that Elohim is coming with might, with His arm ruling for Him. This is the language used to describe Messiah (Isaiah 53:1-12). Paul saw this also (Eph. 1:18-20).
Isa 40:11
Like a shepherd He will tend His flock, In His arm He will gather the lambs, And carry them in His bosom; He will gently lead the nursing ewes.

Isaiah portrays Him as the Good Shepherd also John 10:11-18).
Isa 40:12
Who has measured the waters in the hollow of His hand, And marked off the heavens by the span, And calculated the dust of the earth by the measure, And weighed the mountains in a balance, And the hills in a pair of scales?

Who has done those things? The answer to these rhetorical questions can only be the all powerful Elohim. Mankind has spent thousands of years studying earth's waters and land masses. The "dust of the earth" must mean matter itself. All these things were measured, weighed and balanced by Elohim's hand in no time and with no effort whatsoever. "Measured heaven with a span..." A "span" is the width of a hand. We tend to think that outer space is limitless in it's dimensions. Isaiah tells us it is a hand width to Elohim.

River Valley Torah Assembly