Charles H. Spurgeon on Psalms 146:4

In that very day his thoughts perish. The thoughts which the Psalmist here, no doubt, especially intends are those purposes which are in the minds of great men of doing good to those who are under, and depend upon them. The Hebrew word here used is derived from a verb that signifieth to be bright: cogitationes serenae, those candid, serene, benign, benevolent thoughts which they have of advancing their allies, friends and followers. These thoughts are said to "perish" in "that day" wherein they are conceived; so Tremellius glosses. In which sense the instability of great men's favour is asserted, whose smiles are quickly changed into frowns, love into hatred, and so in a moment their mind being changed, their well wishing thoughts vanish. But more rationally, "their thoughts perish in that day" wherein their persons die, because there is no opportunity of putting their purposes into execution. They perish like the child which comes to the birth, and there is no strength to bring forth; or like the fruit which is plucked off before it be ripe. Whilst they live we may be deceived in our expectations by the alteration of their minds; but, however, their condition is mortal, and when that great change by death comes, their designs (how well so ever meant) must want success. From hence it followeth, which is by some looked upon as a part of the meaning of the words, that the thoughts or hopes of them who trust in them perish. It is a true apothegm, Major pars hominum expectundo moritur; the greatest part of men perish by expectation. And good reason, inasmuch as their expectation, being misplaced, perisheth. How strongly this argument serveth to press the Psalmist's caution against confidence in man, though never so great, is obvious. It is true, princes and nobles being invested with honour, wealth and authority, have power in their hands, and perhaps they may have thoughts in their hearts to do thee good; but, alas, how uncertain is the execution of those intentions, and therefore how foolish is it to depend upon them. "Trust in the Lord Jehovah" (saith the prophet), "for with him is everlasting strength." Aye, and with him is unchangeable goodness. It is safe building upon the rock, trusting upon God, whose thoughts of mercy are (like himself) from everlasting to everlasting; but nothing is more foolish than to build on the sand, trust to men, whose persons, together with their thoughts, perish in a moment. Therefore let our resolution be that of David: "It is better to trust in the Lord than to put confidence in man; it is better to trust in the Lord than to put confidence in princes", Ps 118:8-9. —Nathanael Hardy.