Origen Rom7

"Is it the law of Moses that through which Adam knew his sin and hid himself from the presence of the Lord? Is it the law of Moses through which Cain knew his sin and said, 'My sin is greater than that I should be left alive'
...Rather, it is the law concerning which we have frequently said is in everyone's hearts, 'written not with ink, but by the Spirit of the living God,' and teaches each man what ought to be done and what ought to be avoided. It is the same [law], then, through which a man knows his own sin. For it speaks to us within the conscience and says, 'You shall not covet.'"
--Origen commenting on Rom7 passage