“You shall break them with a rod of iron and dash them in pieces like a potter’s vessel.” -Psalm 2:9
Derek Kidner notes the book of Revelation quotes these words, once concerning the victorious Christian (2:27) and twice concerning his Lord (12:5; 19:15).
King David, and by messianic extension, Jesus Christ, will rule his inheritance effectively and that those who resist his reign will be as weak as a clay jar under the iron rod that is, ultimately, Christ’s rulership.