“I am speaking in human terms, because of your natural limitations. For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification.” -Romans 6:19
All of God’s revelation is a matter of condescension. Human reason cannot attain to God so God must come to us. To do so requires that he make the mysteries of the Trinity understandable to mere human beings if we are to know anything of him. Furthermore, what he has revealed of the heavenly mysteries are (to use a cliché) just the very tip of the iceberg. What God has revealed to man is not all God knows, of course.
Here Paul tells the Christians at Rome that his death-to-life and slavery illustrations are simply everyday examples to make the doctrine more understandable. Jesus says similar to his disciples in John 3:12: If I have told you earthly things and you do not believe, how can you believe if I tell you heavenly things?
Salvation in Christ is a mystery but Paul has been speaking in human terms so they can understand how to live now that they are Christians. To yield one’s members as slaves to impurity and lawlessness only leads to practicing more lawlessness and rendering one unfit for the presence of God (state of condemnation). But to yield one’s members as slaves to righteousness not only leads to sanctification (the process of becoming more Christlike), but it also renders one fit for God’s presence (state of grace).
The theologian, Robert Jewett, explains notes how Paul’s exhortation here points to a new form of social life as the primary embodiment of holiness’. In other words, Paul’s “so now” is more than just an exhortation to personal holiness; he is laying down the principles for life in a new Christian Society.