God, in His sovereignty over all, has appointed all things which are in the present and which will be in the future and seeks to reemploy the things which took place in the past. Whatever God does will be forever; nothing can be added to it, nor can anything be taken from it, that all would fear Him that they may have His wisdom to realize the real meaning of human life (vv. 14-15).
Ecclesiastes 3:16—4:16 is concerned with Solomon's experiment in ranks and classes in human society.
The judgment of God in the appointed time brings the righteous down to the same level as the wicked (3:16-17).
This is for God to prove that men are but beasts, bringing men down to the same level as beasts. Thus, there is nothing better than that a man take his portion to rejoice in his works, for who will bring him to see what will be after him? (vv. 18-22).
The oppressed are in tears and the oppressors have power, but both have no comforter. Solomon praised the dead more than the living and even the more the one who has not yet been and has not seen the evil work under the sun (4:1-3).
All labor and all skill in work cause man's jealousy for his neighbor. The fool folds his hands together and consumes his own flesh. One handful with quietness is better than two hands full with labor. All these are vanity and a chasing after wind (vv. 4-6).
One who is alone and without a second, having no son or brother, labors without end. His eye is not satisfied with riches, but he labors and deprives himself for no one. Two are better than one, and three are even better than two (vv. 7-12).
A poor but wise youth is better than an old and foolish king who no longer knows how to be admonished (vv. 13-16).