Paul offers a sustained argument debunking the outrageous idea that by saying that “when sin increased, grace abounded all the more,” he was suggesting that we should “continue in sin that grace may abound.” His chief argument is that the old, sinning, self has died giving rise to a new righteous life. Sinning is incompatible with this new life. It’s actually the transformation of sinners into righteous people that really highlights God’s grace. 

Such is God’s grace. Not only did he declare you righteous in Jesus, his amazing grace daily transforms you from the sin-ravaged, fearful of death old self into the image of Jesus. This grace is yours if you come to Jesus in faith; his grace is great enough to transform you no matter how great your sins.