Ecclesiastes 2:12

And I went again in search of wisdom and of foolish ways. What may the man do who comes after the king? The thing which he has done before.

Ecclesiastes 1:17

And I gave my heart to getting knowledge of wisdom, and of the ways of the foolish. And I saw that this again was desire for wind.

Ecclesiastes 7:25

I gave my mind to knowledge and to searching for wisdom and the reason of things, and to the discovery that sin is foolish, and that to be foolish is to be without one's senses.

Ecclesiastes 1:9-10

That which has been, is that which is to be, and that which has been done, is that which will be done, and there is no new thing under the sun.

Treasury of Scripture Knowledge

Summary

And I turned myself to behold wisdom, and madness, and folly: for what can the man do that cometh after the king? even that which hath been already done.

Even that which hath been already done

Bible References

I turned

Ecclesiastes 1:17
And I gave my heart to getting knowledge of wisdom, and of the ways of the foolish. And I saw that this again was desire for wind.
Ecclesiastes 7:25
I gave my mind to knowledge and to searching for wisdom and the reason of things, and to the discovery that sin is foolish, and that to be foolish is to be without one's senses.

Even that which hath been already done

Ecclesiastes 2:25
Who may take food or have pleasure without him?

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain