Cosmas Indicopleustes

And these things have been said about his humanity, for it is about his deity that in this very psalm it has been said: Thou shalt rule them with a rod of iron; as a potters vessel shalt thou dash them in pieces; as if at the same time making known the force and might of his divinity, and indicating the renovation or regeneration of the human race—for the potter's vessel, though dashed to pieces, provided it has not as yet been subjected to the furnace, admits of being refashioned.

The Christian Topography, Book 5 ↗

Augustine of Hippo

"You shall rule them with a rod of iron," with inflexible justice, and "You shall break them like a potter's vessel" [Psalm 2:9]; that is, "You shall break" in them earthly lusts, and the filthy doings of the old man, and whatsoever has been derived and inured from the sinful clay.

Exposition on Psalm 2 ↗

Thomas Aquinas

Then when he says, "You shall rule them," the execution of power is set forth. And according to the historical sense, it could be explained that because he was appointed king of the Jews, he also ruled over certain nations that he had subjugated, as a figure of the universal dominion of Christ. …

Exposition on the Psalms of David ↗