Psalms 64:6

They search out iniquities, inventing, planning, evil acts; they accomplish a diligent search, completing the plan which they have conceived. Both the inward thought of everyone of them and the heart is deep, literally, "and the inward part of a man and his heart is deep," the workshop of evil, the place where all the wicked designs are worked out, is hidden from the eves of men like an abyss of dark mystery and brooding wickedness. While, however, they flatter themselves that their scheming is hidden from the eyes of men, the Lord knows their every thought.