All the labor of man - This is the grand primary object of all human labor; merely to provide for the support of life by procuring things necessary. And life only exists for the sake of the soul; because man puts these things in place of spiritual good, the appetite - the intense desire after the supreme good - is not satisfied. When man learns to provide as distinctly for his soul as he does for his body, then he will begin to be happy, and may soon attain his end.
Connect these verses with Ecclesiastes 6:2-3: “All labor is undertaken with a view to some profit, but as a rule the people who labor are never satisfied. What advantage then has he who labors if (being rich) he is wise, or if being poor he knows how to conduct himself properly; what advantage have such laborers above a fool? (None, so far as they are without contentment, for) a thing present before the eyes is preferable to a future which exists only in the desire.”
Ecclesiastes 6:8
What - literally, what profit (as in Ecclesiastes 1:3).
Knoweth living - i. e., “Knows how to conduct himself rightly among his contemporaries.”