in the hand of God. Despite the “under the sun” implications that things on earth seem to happen indifferently to both righteous and unrighteous, Solomon intuitively knew that “the Judge of all the earth” will certainly “do right” (Genesis 18:25) in the scales of eternity.

come alike to all. Since “all have sinned” (note Ecclesiastes 7:20), therefore all deserve nothing good from God. Nevertheless, God has done good to all in countless ways (see Acts 14:17, for example). For the present, “the whole creation groaneth and travaileth in pain together” (Romans 8:22).

dead know not. This does not mean that there is no future life or consciousness after death, but only that nothing more can be done to earn heavenly rewards. Even the greatest men are soon forgotten after they die; thus it is important to make one's brief life span as productive for God as possible.

Live joyfully. Solomon surely still deeply loved Naamah, the “wife of his youth,” though she must have grieved over his later accumulation of his many pagan wives for politico/prestige purpose. In his old age, Solomon could at least give this wise counsel to young men. The word “joyfully” occurs only this once in the Old Testament. One should attempt to keep his marriage alive and happy as long as life continues.

the wife whom thou lovest. Note Proverbs 5:15-19 and Song of Solomon (Introduction) and contrast Ecclesiastes 7:28. In retrospect, King Solomon was well able from his sad experience with multiple wives to urge the far better way of monogamy.

with thy might. Note Colossians 3:23. God does not expect more than we can do, but He does require that we do whatever we can do “heartily, as unto the Lord” and that we do it “with our might.”

time and chance. Evolutionists like to imagine that “time and chance” are sufficient to explain the origin and evolution of all forms of life, including men. These undoubtedly have a role in the vicissitudes of life, but random changes could never produce complex living creatures, no matter how many billions of years might be assumed.

There was a little city. This is probably not a reference to some actual event, but rather a parable. However, a somewhat similar event had really occurred during David's reign (2 Samuel 20:13-22).