I said to the fools, Act not foolishly. [1] After he has set the office of God full in his own view and in the view of the faithful, he now triumphs over all the ungodly, whom he impeaches of madness and blind rage, the effect of their despising God, which leads them to indulge to excess in pride and self-gloriation. This holy boasting to which he gives utterance depends upon the judgment, which in the name of God he denounced to be at hand; for when the people of God expect that he is coming to execute judgment, and are persuaded that he will not long delay his coming, they glory even in the midst of their oppressions. The madness of the wicked may boil over and swell with rage, and pour forth floods to overwhelm them; but it is enough for them to know that their life is protected by the power of God, who can with the most perfect ease humble all pride, and restrain the most daring and presumptuous attempts. The faithful here deride and despise whatever the wicked plot and conspire to execute, and bid them desist from their madness; and in calling upon them to do this, they intimate that they are making all this stir and commotion in vain, resembling madmen, who are drawn hither and thither by their own distempered imaginations. It is to be observed, that the Psalmist represents pride as the cause or mother of all rash and audacious enterprises. The reason why men rush with such recklessness upon unlawful projects most certainly is, that blinded by pride, they form an undue and exaggerated estimate of their own power. This being a malady which is not easily eradicated from the hearts of men, the admonition, Lift not up your horn on high [2] is repeated once and again. They are next enjoined not to speak with a fat or a stiff neck; by which is meant that they should not speak harshly and injuriously; for it is usual with proud persons to erect the neck and raise the head when they pour forth their menaces. Others translate the words, Speak not stiffly with your neck; but the other translation is the more correct.

Footnotes

1 - "Or, Be not mad." The verb is thvlv, tahollu, from hll, halal, he was mad, boasting -- Bythner

2 - Lift not up your horn on high, that is, bear not yourselves insolently, from a false notion of your power, (comp. Amos 6:13.) It has been supposed that the metaphor is taken from the manner in which horned animals carry themselves when they are in an excited state. A practice among the Abyssinians, described by Mr Bruce, has been also adduced as throwing light upon this verse. He observes, that the governors of the provinces in Abyssinia wear a broad fillet round their heads, which is tied behind the head. In the middle of this fillet is a horn, or a conical piece of silver, gilded with gold; and shaped like our candle-extinguishers. This is called kirn or horn; and is only used in reviews or processions after victory. The way in which they throw back the head when wearing this ornament (lest it should fall forward) gives a stiffness to the position of the head; and this seems to explain the language of the Psalmist, when he mentions speaking with a stiff neck. Instead of with a stiff neck, Parkhurst translates with a retorted neck; observing, that "this is a well-known gesture of pride, contempt, or disdain."

I said unto the fools - To the wicked people in rebellion. Folly and wickedness in the Bible are synonymous terms, as they are identical in fact. See the notes at Psalm 14:1.
Deal not foolishly - Acts not foolishly; carry not out your wicked plans. Do not pursue your schemes of wickedness and folly, for they cannot be successful, and they will only tend to involve you in ruin.
And to the wicked - The wicked people engaged in rebellion - either against a lawful human government, or against God.
Lift not up the horn - The horn is a symbol of strength. Compare Job 16:15; Daniel 7:7-8, Daniel 7:11, Daniel 7:21; Daniel 8:5, Daniel 8:8-9, Daniel 8:21. This is to be understood as the language of the person represented as speaking in the psalm - whether a prince, or whether God himself. It is counsel addressed to the wicked, that they should not attempt to put forth their strength in the accomplishment of their evil purposes. The reason given for this is stated in Psalm 75:6, namely, that success does not depend on chance, or on human power, but must come from God.

I said unto the fools - I have given the idolatrous Chaldeans sufficient warning to abandon their idols, and worship the true God; but they would not. I have also charged the wicked, to whom for a season I have delivered you because of your transgressions, not to lift up their horn - not to use their power to oppress and destroy. They have, notwithstanding, abused their power in the persecutions with which they have afflicted you. For all these things they shall shortly be brought to an awful account. On the term horn, see the note on Luke 1:69.

I said unto the fools,.... To the vain gloriosos, proud boasters, mockers, and scoffers at the day of judgment, and burning of the world:
deal not foolishly; by glorying in themselves, boasting of their riches, and trusting in them; singing a requiem to themselves on account of their abundance, and by putting away the evil day far from them:
and to the wicked, lift not up the horn; of power, grandeur, and wealth, and use it to the injury of others; or be so elated with it as to look with disdain on others; or imagine they shall always continue in this exalted state, as antichrist the horned beast does, Revelation 18:7, the allusion is to horned beasts, particularly harts, which lift up their heads and horns in great pride (p): the phrase signifies to behave proudly and haughtily.
(p) Vid. "Suidam in voce"

Here the writer speaks in view of God's declaration, warning the wicked.
Lift . . . up the horn--to exalt power, here, of the wicked himself--that is, to be arrogant or self-elated.

I said - I charged them. Deal not - Desist from your practices. Lift not up - Do not carry yourselves scornfully and maliciously.