John Gill Commentary Ecclesiastes 8:16

"When I applied my heart to know wisdom, and to see the business that is done upon the earth (for also there is that neither day nor night seeth sleep with his eyes)," — Ecclesiastes 8:16 (ASV)

When I applied mine heart to know wisdom The nature and causes of things; the wisdom of God in his providence, and the grounds and reasons of his various dispensations towards the children of men: the Targum interprets it, the wisdom of the law;

and to see the business that is done upon the earth ; either the business of Providence, in dealing so unequally with the righteous and the wicked, before observed; and which is a business very afflictive and distressing for curious persons to look into, not being able to account for it:

or the labour and toil of men to get wealth and riches, and to find happiness in them;

(for also [there is that] neither day nor night seeth sleep with his eyes) ; or has any sleep in his eyes, through his eager pursuit after worldly things, or, however, has but little; he rises early and sits up late at his business, so close and diligent is he at it, so industrious to obtain riches, imagining a happiness in them there is not:

or else this describes persons curious and inquisitive into the affairs of Providence, and the reasons of them; who give themselves no rest, day nor night, being so intent upon their studies of this kind; and perhaps the wise man may design himself.