Solomon teaches that success lies only in the hands of God. We are given to do our work in the present, but we cannot control the future. He tells us that we should receive a quiet and peaceful heart and commit everything to God. Some fools respond by saying, “Then let us do no work.” When Solomon teaches us to reject our counsels and anxieties, but to do the work, then fools either fall into despair or become prideful. When their plans are thwarted they despair. When their plans succeed they become presumptuous.
Similarly, the Gospel teaches an alien righteousness earned by the merit of Jesus Christ and freely received by faith. The fool responds, “Then let us not do any good works. If faith is sufficient, let us sin.” When we teach about the fruits of faith and true good works, the fool trusts in them for salvation.
Solomon attempts to teach about the meaningful life of the Christian, who gives thanks for the gift of salvation. He is not concerned about the future, but is content with his present vocation. The grace of God provides an abundance of gifts, including daily provisions and satisfaction in the work of his daily vocation(Eccl 2:24-25).