Ecclesiastes 8:16-17 says:
16I carefully studied the things people do in this life. I saw how busy people are. They work day and night, and they almost never sleep. 17I also saw the many things that God does. And I saw that people can’t understand all the work that God does on earth. A person might try and try to understand, but he can’t. Even if a wise man says he understands the work God does, it is not true. No person can understand all those things. (Easy-to-Read Version)
King James Version: 16When I applied mine heart to know wisdom, and to see the business that is done upon the earth: (for also there is that neither day nor night seeth sleep with his eyes:) 17Then I beheld all the work of God, that a man cannot find out the work that is done under the sun: because though a man labour to seek it out, yet he shall not find it; yea farther; though a wise man think to know it, yet shall he not be able to find it.