He shall cut off the spirit of princes - That is, He will cut down their pride; he will break them down. Luther renders it, “He shall take away the wrath of princes.” The allusion is to what he had done as celebrated in this psalm. He had shown that he could rebuke the pride and self-confidence of kings, and could bring them low at his feet.
He is terrible to the kings of the earth - When they are arrayed against him.
(1) they are wholly under his control.
(2) he can defeat their plans.
(3) he can check them when he pleases.
(4) he can, and will, make their plans - even their wrath - the means of promoting or carrying out his own purposes.
(5) he will allow them to proceed no further in their plans of evil than he can make subservient to the furtherance of his own.
(6) he can cut down the most mighty of them at his pleasure, and destroy them forever.