What does the rod of iron in Psalm 2:9 refer to?
The rod of iron refers to the Son's coming judgment upon the nations during the Tribulation. He will break the world's nations with it and dash them in pieces like a potter's vessel. This judgment will culminate at Armageddon, when His rule and reign over the earth are established.
Les explains that Psalm 2:9 backs up in the timeline to the Tribulation. The ones broken with a rod of iron are the nations of the world, not only the Jew, for verse 8 promises the heathen as the Son's inheritance and the uttermost parts of the earth as His possession. They will be dashed in pieces like a potter's vessel, and this breaking will culminate at Armageddon. The passage is set within the Father speaking to God the Son, pointing to His rule and reign here on the earth.
Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter’s vessel.