For brass I will bring gold; rather, for copper. "Brass" was an alloy little known to the Oriental nations. The general idea is that the glorious age of Solomon would return (1 Kings 10:21, 1 Kings 10:27), and Zion be as resplendent and as wealthy as in his time.
The material splendour is, no doubt, throughout the whole description, typical in the main of spiritual glories and excellences. I will also make thy officers peace, and thine exactors righteousness.
"Peace" and "righteousness" are here personified; and the declaration is that they shall bear rule in the community whereof the prophet is speaking (comp, Isaiah 32:16, Isaiah 32:17).