14 And he showed that in the days of those kings, who shall arise in the kingdom, the God of heaven will set up a kingdom which shall not be destroyed and shall not pass away for ever. This is the Kingdom of King Messiah, which is that which shall cause the fourth kingdom to pass away. And above he said:— You saw a stone which was cut out, but not by hands; and it smote the image upon its feet of iron and potter's clay and broke them to pieces. Now he did not say that it smote upon the head of the image, nor on its breast and arms, nor yet on its belly and thighs, but on its feet; because that, of the whole image, that stone when it comes will find the feet alone.
And in the next verse he said:— The iron and the brass and the silver and the gold were broken to pieces together. For after them, when King Messiah shall reign, then He will humble the fourth kingdom, and will break the whole image; for by the whole image the world is meant. Its head is Nebuchadnezzar; its breast and arms the King of Media and Persia; its belly and thighs the King of the Greeks; its legs and feet the kingdom of the children of Esau; the stone, which smote the image and broke it, and with which the whole earth was filled, is the kingdom of King Messiah, Who will bring to nought the kingdom of this world, and He will rule for ever and ever.
Source: Demonstrations (New Advent)