Albert Barnes Commentary Ecclesiastes 9:1

"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." — Ecclesiastes 9:1 (ASV)

A good man’s trust in God is set forth as a counterpoise to our Ignorance of the ways of Providence.

In the hand of God — Under His special protection (Deuteronomy 33:3 and following) as righteous, and under His direction (Proverbs 21:1) as people.

No man ... — Literally, man does not know both love and also hatred: all are before them.

Love and hatred here mean the ordinary outward tokens of God’s favor or displeasure, that is, prosperity and adversity. The phrase Man knoweth not probably means: “man does not know whether to expect prosperity or adversity from God; all his earthly future is in obscurity.”