Thou shalt also suck the milk of the Gentiles... — The metaphor is bold, but the prophet had already presented it in a less startling form in Isaiah 49:23. What is meant in either case is that the new Jerusalem shall be supported by the offerings of the Gentiles.
Related Commentaries of Isaiah 60:16
Isaiah 60:16
16 Thou shalt also suck the milk of the Gentiles, and shalt suck the breast of kings: and thou shalt know that I the LORD am thy Saviour and thy Redeemer, the mighty One of Jacob.