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. Isaiah 60:16
"Milk" is symbolic of wealth and God’s blessing. Among the pastoral people a man’s wealth is measured by the number of his sheep and goats, and by the large cauldrons in which milk is boiled. The Hebrews and the nations that were around about them were all pastoral people whose medium of exchange was butter, cheese, sheep, and goats. The prophets spoke and wrote in the terms of speech which were common expressions and well understood by the simple folk. Today we speak of gold, silver, stocks, oil fields, and coal mines.
"The milk of the Gentiles" means the wealth of the Gentiles. The Jews who were carried away captive were to find favor in the eyes of the Gentile kings and princes. The Gentiles were to give precious gifts of silver and gold to the exiles who were to return to
In Eastern languages, when people offer lavish gifts and generous assistance to others, or are robbed of their goods, it is said, "They have been milked." (Lamsa, George M. 1964. Old Testament Light.