Verse 4
He deviseth mischief upon his bed - He seeks the silent and undisturbed watches of the night, in order to fix his plans of wickedness.
He setteth himself - Having laid his plans he fixes his purpose to do what is bad; and he does it without any checks of conscience or abhorrence of evil. He is bent only on mischief, and lost to all sense of God and goodness. A finished character of a perfect sinner.