Ecclesiastes 2:12

And I turned to see wisdom, and madness, and folly, but what is the man who cometh after the king? that which is already -- they have done it!

Ecclesiastes 1:17

And I give my heart to know wisdom, and to know madness and folly: I have known that even this is vexation of spirit;

Ecclesiastes 7:25

I have turned round, also my heart, to know and to search, and to seek out wisdom, and reason, and to know the wrong of folly, and of foolishness the madness.

Ecclesiastes 1:9-10

What is that which hath been? it is that which is, and what is that which hath been done? it is that which is done, and there is not an entirely 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 give my heart to know wisdom, and to know madness and folly: I have known that even this is vexation of spirit;
Ecclesiastes 7:25
I have turned round, also my heart, to know and to search, and to seek out wisdom, and reason, and to know the wrong of folly, and of foolishness the madness.

Even that which hath been already done

Ecclesiastes 2:25
For who eateth and who hasteth out more than I?