For sin shall not be master over you, for you are not under law but under grace.
This verse sounds like a call back to Genesis and God speaking with Cain. God tells Cain that sin is at his door and its desire is for him, but Cain must be master over it (Genesis 4:7). Paul seems to be echoing that statement. In the original, God presents Cain with the instruction: If you do well, surely you will be accepted. Paul is saying much the same thing when he says for you are not under law but under grace. Paul is pointing out that the believer lives under a different standard and covenant and in a whole new relationship with God than has been available since Eden.
What follows is, I fear, muddled due to me still parsing the ideas.
Lately, I have been wrestling with the concomitants of a particular decision. As I am unsure how to speak of it in general terms, I will simply state that the decision brings along with it a measure of fear. Until recently, I had thought the fear might be an indicator that the decision needed more prayer and consideration. As I was thinking on it and speaking with God of my concerns, He reminded me that the fear of Him is the beginning of wisdom and I felt encouraged to reconsider the fear. The fear in question is such as would, if embraced, act as a deterrent to sin. More, I realized that the fear is not of committing the sin, but of potentially “getting away with it.” If I were to sin without being disciplined, that would be terrifying and I would question whether or not I had ever truly trusted in Christ to save me. How does this relate to Paul’s statement that sin shall not be master over me or that I am not under law but under grace? Quite well, as it turns out.
The fear of “getting away with” something was always present with my parents. I would do something against their rules and be afraid that I would get caught, but more afraid that I would not. To not get caught meant a lapse; a break in their watch over me. I did not want that with them and I want it still less with my God.
Likewise, a fear that leads to repentance — which is, at its core, a turning away from sin and turning to God — is exactly the kind of fear that leads to wisdom. It is the healthy, proper fear of the LORD. The fear that leads to a renunciation of sin, even in the hypothetical, is good and right and pure. It is akin to the fear that tells me not to get too close to the edge of a cliff or the fear that tells me I should not taunt the bear. Neither is a good idea. Neither is likely to end well for me (though the bear might be happier in the aftermath).
Let me live in the covenant of grace; a relationship with God that allows me to be rightly afraid of damaging the relationship.