Baptism.
Paul argues that two things happen in our baptism. First, we join with Christ in his death, burial, and resurrection. Our baptism demonstrates our recognition of what Jesus did for us. It is the means by which we too die to self and allow God to raise us to a new life. Second, baptism allows us to know with certainty that we have moved from the sphere of slavery to sin into the sphere of slavery to God. Paul’s point is that we are going to be slaves to something. We will either be slaves to sin and having to live to keep every law or we will be slaves to God and his grace so that we can live righteously. We either respond to sin or respond to grace. Our baptism is a tangible line of distinction for a changed heart and life. It may take years to appreciate and grow into the fullness of spiritual maturity but the reality remains. We are no longer under the oppression of sin and the fear of death. Because of our baptism God is our Master and we find life in his grace. We respond to God’s grace with faith and righteous living because He is the one who has set us free from the oppressive master of sin. We died and God has made us alive. Thanks be to God.