Matthew Henry Commentary Ecclesiastes 9:1-3

"For all this I laid to my heart, even to explore all this: that the righteous, and the wise, and their works, are in the hand of God; whether it be love or hatred, man knoweth it not; all is before them. All things come alike to all: there is one event to the righteous and to the wicked; to the good and to the clean and to the unclean; to him that sacrificeth and to him that sacrificeth not; as is the good, so is the sinner; [and] he that sweareth, as he that feareth an oath. This is an evil in all that is done under the sun, that there is one event unto all: yea also, the heart of the sons of men is full of evil, and madness is in their heart while they live, and after that [they go] to the dead." — Ecclesiastes 9:1-3 (ASV)

We are not to think our searching into the word or works of God is useless simply because we cannot explain all difficulties. We may learn many things that are good for ourselves and useful to others.

But man cannot always decide who are the objects of God's special love, or who is under his wrath; and God will certainly make a distinction between the precious and the vile in the world to come. The difference regarding present happiness arises from the inward supports and consolations the righteous enjoy, and the benefit they derive from varied trials and mercies.

As far as the sons of men are left to themselves, their hearts are full of evil; and prosperity in sin even causes them to defy God through daring wickedness. Though in this life the righteous and the wicked may often seem to fare alike, after death there will be a vast difference between them.