And I gave my heart to seek and search out by wisdom concerning all things that are done under heaven: this sore travail hath God given to the sons of man to be exercised therewith. I gave my heart to ... search out by wisdom concerning all (things) that are done under heaven. "Search" implies a deals investigation into the results gained by all the labours done under the sun.
This sore travail hath God given - i:e., sore vexation, namely, the wisdom which consists in testing thoroughly, etc.; that of 'searching out all things done under heaven.' Wisdom busied about merely earthly things brings only pain.
To be exercised therewith - i:e., disciplined; literally, 'that they may thereby chastise or humble themselves.