Albert Barnes Commentary Psalms 39:6

"Surely every man walketh in a vain show; Surely they are disquieted in vain: He heapeth up [riches], and knoweth not who shall gather them." — Psalms 39:6 (ASV)

Surely every man walketh in a vain show - Margin, “an image.” The word rendered “vain show”—צלם tselem—means properly a shade, a shadow; and then, an image or likeness, as representing any real object. Then it comes to denote an idol (2 Kings 11:18; Amos 5:26). Here the idea seems to be that of an image, as distinguished from a reality; the shadow of a thing, as distinguished from the substance. Man seems to be like an image, a shadow, a phantom—and not a real object, walking about. He is a form, an appearance, that soon vanishes away like a shadow.

Surely they are disquieted in vain - That is, they are actively engaged; they bustle about; they are full of anxiety; they form plans which they execute with much toil, care, and trouble; yet for no purpose worthy of so much diligence and anxious thought. They are busy, bustling “shadows”—existing for no real or substantial purposes, and accomplishing nothing. “What shadows we are, and what shadows do we pursue,” said the great orator and statesman, Edmund Burke; and what a striking and beautiful comment on the passage before us was that saying, coming from such a man, and from one occupying such a position.

He heapeth up riches - The word used here means to heap up, to store up, as grain (Genesis 41:35); or treasures (Job 27:16); or a mound (Habakkuk 1:10). Here it undoubtedly refers to the efforts of men in accumulating wealth, or storing up property. This was the thing which struck the psalmist as the leading employment of these moving shadows—a fact that would strike anyone as he looks upon this busy world.

And knoweth not who shall gather them - Who shall gather them to himself; to whom they will go when he dies. (Ecclesiastes 2:18, 2:21; Ecclesiastes 5:13–14; Luke 12:20).

The idea is that it is not only vanity in itself to attempt to accumulate property as the great business of life—since this is not what the great object of life should be, and a life thus spent really amounts to nothing—but it is also vanity in this respect: a man can have no absolute control over his property when he is dead, and he does not know, and cannot know, into whose hands his accumulated gains may fall.

The facts on this subject—the actual distribution of property after a person dies, the use often made of it, against which no one can guard—should, together with other and higher motives, be a powerful consideration for everyone not to make amassing wealth the great business of life.