He shall have dominion also from sea to sea. It does not appear that any particular seas are meant, as in Exodus 23:31 and Numbers 34:3, Numbers 34:6; rather, the idea is that the earth is set in the midst of the sea, and that Messiah's dominion will reach from shore to shore.
And from the river (i.e. the Euphrates) unto the ends of the earth. Israel's promised dominion extended only as far as the great river (Genesis 15:18), which was also the boundary of Solomon's kingdom eastward (1 Kings 4:21, 1 Kings 4:24); Messiah's was to reach indefinitely beyond the river to the world's end.