Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil.
The prosperity of the wicked is not only an evil in itself, but it leads the way to a more deliberate and unrestrained course of sin. The fact that the Divine sentence that condemns evil is not executed speedily, leads many to think that they can sin with impunity. They do not see that the slowness with which the messenger of vengeance often travels gives opportunity for repentance and amendment before the stroke of punishment falls. Men think they are secure, and give themselves fearlessly to the practice of evil. Yet the Preacher could not give up his conviction that punishment of evil was but delayed and not averted. Though he saw the sinner do evil a hundred times and prolong his days, he knew that the righteousness of God, which in the present world seems so often obscured and thwarted, would in the end assert itself (ver. 12). Though the sinner enjoyed prosperity, it was a deceitful calm before the storm; but the righteous who truly feared God had a peace of spirit which no outward misfortunes or persecutions could disturb. "Appearances, the Preacher saw clearly enough, were against him, yet his faith was strong even under all such difficulties, and through it he was victorious" (Wright) (cf. 1 John 5:24). The prosperity of the wicked is, after all, only apparent. It has no sure foundation; can anticipate no long duration. His days may be many in number, but they soon pass away "as a shadow;" and when the last comes, every wish for prolonged life will be in vain. He may be at the very height of enjoyment when the hour strikes for his enforced departure from the world in which he has abused the long-suffering of God; and no prayers or entreaties or struggles will avail to prolong his days. The shadow on the dial cannot be forced to retrace its course, or to journey more slowly. "His breath goeth forth, he returneth to his dust; in that very day his thoughts perish." - J.W.
Parallel VersesKJV: Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil.