Then shall he speak unto them - That is, this seeming indifference and unconcern will not last forever. He will not always look calmly on, nor will he suffer them to accomplish their purposes without interposing. When he has shown how he regards their schemes - how impotent they are, how much they are really the objects of derision, considered as an attempt to cast off his authority - he will interpose and declare his own purposes - his determination to establish his king on the hill of Zion. This is implied in the word "then."
In his wrath - In anger. His contempt for their plans will be followed by indignation against themselves for forming such plans, and for their efforts to execute them. One of these things is not inconsistent with the other, for the purpose of the rebels may be very weak and futile, and yet their wickedness in forming the plan may be very great. The weakness of the scheme, and the fact that it will be vain, does not change the character of him who has made it; the fact that he is foolish does not prove that he is not wicked. God will treat the scheme and those who form it as they deserve - the one with contempt, the other with his wrath. The word "wrath" here, it is hardly necessary to say, should be interpreted in the same manner as the word "laugh" in Psalm 2:4, not as denoting a feeling precisely like that which exists in the human mind, subject as man is to unreasonable passion, but as it is proper to apply it to God - the strong conviction (without passion or personal feeling) of the evil of sin, and the expression of his purpose in a manner adapted to show that evil, and to restrain others from its commission. It means that he will speak to them as if he were angry; or that his treatment of them will be such as men experience from others when they are angry.
And vex them - The word here rendered "vex" - בהל bâhal - means in the original or Qal form, to tremble; and then, in the form used here, the Piel, to cause to tremble, to terrify, to strike with consternation. This might be done either by a threat or by some judgment indicative of displeasure or anger. Psalm 83:15; Daniel 11:44; Job 22:10. The idea here is that he would alarm them, or make them quake with fear, by what is specified of his purpose; to wit, by his determination to set his King on his holy hill, and by placing the scepter of the earth in his hands. Their designs, therefore, would be frustrated, and if they did not submit to him they must perish (see Psalm 2:9-12).
In his sore displeasure - literally, in his "heat" or "burning," that is, in his anger; as we speak of one that is inflamed with anger, or that burns with indignation; or, as we speak of the passions, kindling into a flame. The meaning here is, that God would be displeased with their purposes, and that the expression of his design would be adapted to fill them with the deepest alarm. Of course, all such words are to be interpreted in accordance with what we know to be the nature of God, and not in accordance with the same passions in men. God is opposed to sin, and will express his opposition as if he felt angry, but it will be in the most calm manner, and not as the result of passion. It will be simply because it ought to be so.

Then shall he speak unto them in his wrath - He did so to the Jews who rejected the Gospel, and vexed and ruined them by the Roman armies; he did so with the opposing Roman emperors, destroying all the contending factions, till he brought the empire under the dominion of one, and him he converted to Christianity viz., Constantine the Great.

(c) Then shall he speak unto them in his wrath, and vex them in his sore displeasure.
(c) God's plagues will declare that in resisting his Christ, they fought against him.

Then shall he speak unto them in his wrath,.... Or, "and he shall speak to them"; so Noldius: that is, the Lord that sits in the heavens, and laughs, and has the Heathen, the people, the kings and rulers in derision, shall not only silently despise their furious and concerted opposition to him and his Messiah, but shall at last speak out unto them, not in his word, but in his providences; and not in love, as to his own people, when he chastises them, but in great wrath, inflicting severe and just punishment. It seems to refer to the destruction of Jerusalem, after the crucifixion, sufferings, death, resurrection, and ascension of Christ; and after the pouring out of the Spirit, and when the Gospel, to their great mortification, had got ground, and made large advances in the Gentile world;
and vex them in his sore displeasure; or "in the heat of his anger" (e): see Deuteronomy 29:24, where the Holy Ghost speaks of the same people, and of the same ruin and destruction of them at the same time, as here: and as the carrying of the Jews captive into Babylon is called their vexation, Isaiah 9:1; much more may their destruction by the Romans; then it was they howled for vexation of spirit, Isaiah 65:14; the wrath of God came upon them to the uttermost; they were filled with trouble and confusion, with terror and consternation, as the word (f) used signifies; they were vexed to see themselves straitened and pent in on every side by the Roman armies, oppressed with famine and internal divisions, rapine and murder; to see their temple profaned and burnt, their city plundered and destroyed, and themselves taken and carried captive: and what most of all vexed them was, that their attempts against Jesus of Nazareth, the true Messiah, were fruitless; and that, notwithstanding all their opposition to him, his name was famous, his interest increased, his kingdom was enlarged, through the spread of his Gospel among the Gentiles; and what Jehovah in Psalm 2:6 says, though it is to the comfort of his people, was to their terror and vexation.
(e) "in aestu irae suae", Junius & Tremellius. (f) "conturbabit", V. L. Vatablus, Gejerus; so Musculus; Junius & Tremellius, Piscator; "terrebit", Pagninus, Montanus; so Cocceius, Michaelis; see Ainsworth.

Then shall he speak--His righteous indignation as well as contempt is roused. For God to speak is for Him to act, for what He resolves He will do (Genesis 1:3; Psalm 33:9).
vex them--agitate or terrify them (Psalm 83:15).