That brings us to Paul's question: "Shall we continue in sin that grace may abound?" to which he quickly gave the emphatic answer "Certainly not!" (Rom 6:1-2). Some in Paul's day apparently suggested that continuing to live in sinfulness could have a good effect in that it would allow God's grace to shine forth all the more. What a convoluted line of reasoning! Such an attitude demonstrates a lack of appreciation for the dangers of sin and a lack of respect for what God did in sending Jesus to the cross. It further demonstrates a poor understanding of repentance, for repentance is a change of mind that leads to a change of life that results in turning away from sinfulness (Acts 3:19). The idea that sinning will somehow glorify God by allowing Him to further demonstrate His grace is a notion spawned by the devil!
A variant to this line of reasoning deals with sins of carelessness rather than of purposefulness. Some people don't specifically plan to sin, but they have the attitude that sinning is not that big a deal. They don't feel the need to be all that discerning as to what is and what is not sinful, for if they make a mistake, they reason, God's grace will cover it. Such an attitude toward sin is careless and reckless. It is pure folly and demonstrates a lack of respect for the seriousness of sin.
This is exactly opposite the mindset that Paul admonished when he instructed the Ephesians to "walk circumspectly," that is with extreme caution, "because the days are evil" (Eph 5:15-16). Perhaps Paul was referring to this group in his follow up question later in Romans chapter six: "Shall we sin because we are not under law but under grace?" Once again he quickly answered his own question: "Certainly not!" (Rom 6:15).
We can neither go on sinning willfully, nor can we carelessly stroll through the minefields of sin in this world, simply expecting god's grace to take care of us. Such attitudes cheapen the grace of God. We must take literally Paul's question and answer: "Shall we continue in sin that grace may abound? Certainly not!"