We Are Therefore No Longer To Be Servants Of Sin, But Servants Of Righteousness And Of God, No Longer Earning Death As Our Wages, But Receiving The Free Gift Of Eternal Life In Christ Jesus Our Lord (6:15-23).
The question now is, ‘If we are not under the Law but under grace, does that mean that we can sin freely?' To those who understand what it means to be ‘under grace' the question answers itself. As has already been emphasised to be ‘under grace' is to be within the sphere of the loving activity of God which is at work to deliver us from sin (Romans 5:2). It is to be accepted as righteous before God through the righteousness of the One Who died for us (Romans 5:15). It is to be enjoying the new life that He has given us (Romans 5:17). It is to be under His formative care (Romans 5:20). It is to have died with Christ and be living with Him in newness of life (Romans 6:1-11). It is to acknowledge His rights over us. How can someone who is in that position easily sin? To sin easily would simply indicate that we are not God's servants at all. For what we are ‘under' is demonstrated by whom we obey.
So Paul answers the question in terms of servitude. The test of what you are under is determined by ‘who' you obey, whether sin (which results in death) or obedience (which results in righteousness); whether uncleanness and deep iniquity, or righteousness; whether sin or God. And the end of the one is death, whilst the end of the other is righteousness and life.