History: Ludlow provides historical background:
The Medes came from Persia and easily conquered Babylon in 538 B.C. The walls were destroyed twenty years later, after which the city never again became the capital of an independent, strong Mesopotamian power. Two centuries later, after the Greeks, under Alexander the Great, conquered the Persians, Babylon rapidly declined in commercial and cultural importance as Seleucia became the major city in the area. By the time of Christ, only a few astronomers and mathematicians continued to live in the ancient, sparsely populated city. After they left, Babylon remained a deserted tell (mound), which sand and brush gradually covered until it became a hill used only by wild animals and as grazing land for nomadic flocks.
Scripture: Isaiah’s important point is the Medes’s lack of regard for silver and gold. Not only is this a reversal of the usual veneration of wealth, but it also affirms that the wealthy cannot purchase salvation. The forces arrayed against them (literally the Medes, symbolically the righteous) will value the Messiah’s cause, not money.