Albert Barnes Commentary Job 21:27

"Behold, I know your thoughts, And the devices wherewith ye would wrong me." — Job 21:27 (ASV)

Behold, I know your thoughts—That is, “I see that you are not satisfied, and that you are still disposed to maintain your former position. You will be ready to ask, Where are the proofs of the prosperity of the wicked? Where are the palaces of the mighty? Where are the dwelling places of ungodly men!”

And the devices which you wrongfully devise against me—The course of sophistical argument which you pursue, the tendency and design of which is to prove that I am a wicked man. You artfully lay down the position, that the wicked must be, and are in fact, overwhelmed with calamities, and then you infer, that because I am overwhelmed in this manner, I must be a wicked man.