The Knowledge Of Sin

Romans 3:19-20 NASB

Now we know that whatever the Law says, it speaks to those who are under the Law, so that every mouth may be closed and all the world may become accountable to God; because by the works of the Law no flesh will be justified in His sight; for through the Law comes the knowledge of sin.

When Adam ate from the tree of the knowledge of good and evil, sin entered the world. The digested fruit becomes the Law given to Israel, his descendants and heirs who are to tend to the Garden and hold out the light of God to the nations and the world. 

 The Law applies to those under the Law. 

Those who are in Christ have been freed from the Law, but have not been freed from obedience to the Lord. It is now a personal matter. Fortunately, we have the person of Jesus Christ who is with us and intercedes with the Father on our behalf.