To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law. To those outside the law I became as one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law. (1Co 9:19-20)
I'm not trying to reopen a debate on the nature of the Old Testament Law to the New Testament believer... but I did think this was a helpful insight.
Paul, in the midst of his discourse on how he has become all things to all men in order to win them, mentions, almost as an aside, his relationship to the law. This gives a valuable insight into our relationship to it too:
We are not under the law
We are not outside of the law
We are under the law of Christ
Although we are no longer under the law, we are not outside of it either. It still applies to us as it finds its fulfilment in Christ. All of the law must pass through Christ before it applies to us.
Some of the law gets added to, because the real issue is one of the heart and not of observance of the letter. e.g. the commandments against adultery and murder.
Some of the law does not pass through because it has already been ultimately fulfilled in Christ. e.g. the sacrifices for sins, the cutting off of the flesh in circumcision.
Some of the law becomes a matter of conscience, because it was to illustrate a principle that is now better illustrated in the New Covenant realities, and the issue is not one of observance, but of faith. e.g. eating or not eating certain foods, observing or not observing special days.
And some of the law passes through unchanged. e.g. honouring ones father and mother.
Whilst we might disagree on the finer details of interpretation and application there are some things that are very clear:
First, no-one is justified by observing the law. We cannot earn our salvation or favour with God by observing the law. We are saved by grace alone, through faith alone, in Christ alone.
However, those who love God will obey his commandments. Whilst we cannot earn favour by obedience, we can grieve the Holy Spirit by disobedience.
A correct understanding of the law plays an important part of our walk of faith. It makes the difference between observance and obedience on the one hand, and between liberty and licence on the other.
We know that the law is good if one uses it properly. (1Ti 1:8 NIV)