Here's my take on the Law.
The basics__
First the basics. The Law was given in the Old Testament to show God's standards of righteousness--love and obedience to God. But it was given as a set of rules for us to obey on our own strength. And obeying these rules on our own is something none of us can do. So what the Law ended up doing was showing very clearly that we cannot live up to God's Law, his standards of righteousness.
The Law shows us that we are all sinners (Rom. 3:19-20). So we need a way to be saved from our sin. In the Old Testament God provided animal sacrifices for the forgiveness of sins. These symbolically looked forward to Jesus Christ, the perfect sacrifice. But the meaning of animal sacrifices was not fully revealed to people in the Old Testament. Why not?
Because God was still teaching humanity (specifically his chosen people, the Jews) the lesson of the Law--the lesson that we all fall short of God's standards. Only when this lesson had been taught would the next lesson be fully revealed--grace.
Grace is salvation based on faith and not on works of the Law. Grace was active in the Old Testament, but it was fully revealed only in the New Testament.
Grace was needed for the people of the Old Testament, since without it they could not be saved. The animal sacrifices could not save them; they were only a symbol of Christ, the true sacrifice to come. Just as God saves people by faith in our time, so also in the Old Testament, while the Law was in effect, God was at the same time quietly saving people based on their faith--which is grace. I say "quietly" because God was doing it beneath the surface, so to speak. Although he saved people by grace, he did not fully reveal the true nature of grace to them, because he wanted them to focus on the law, so they could learn the lesson of the law--that none of us can measure up (Gal. 3:23-25).
So for centuries under the Old Covenant people tried to follow the law, and they learned how wearisome and impossible it was to try to attain righteousness through their own efforts. Finally grace came with Jesus Christ, and we were set free from the law (Rom. 7:3-4).
Do Christians today still need to obey the Law?__
However, there are some who say that we today are not free from the Law--that we still have to obey the Law in whole or in part. Maybe not for salvation, but at least as the guidelines for how we should live today. After all, don't the Ten Commandments still apply to us? Just because we're now under grace, does that mean we are free to steal and commit adultery and murder?
No. We?re not free to commit those sins. But it's not because we're still under the law. The reason we still don't commit those sins is because now we're supposed to live by love, guided by the Holy Spirit (Gal. 5:4-6).
Under grace we no longer try to live by any written set of rules. Rules such as those found in the Law are meant to appeal to our own ability to simply hear those rules and live them out on our own power. But under grace we don't live on our own power. We live by the Holy Spirit (Rom. 8:3-4). It's as if when we're saved, the Holy Spirit comes in and says, "Okay, I'll run things now. You don't have to go by the Law any more." We're now under love, not the Law. But the Law and the rule of love in the Spirit do have a lot in common--under love we still don't murder, etc. Not because we're following the Law, but because we're following the new way of living by the Spirit, and that way of living also does not murder, etc.
So the Law and love have a lot in common. That's why when we follow love we're also fulfilling the Law (Rom. 13:8). We?re not following all the various commandments of the Law, but we?re following the basic meaning of the Law, which is love. As Jesus said, the greatest commandments of the Law are to love God and love your neighbor as yourself (Matt. 22:35-40). But the Law went about doing these things by concentrating on rules. Now that we have the Spirit, we go about loving God and our neighbor by concentrating on the attitudes of the heart. We don?t follow the letter of the Law (2 Cor 3:6), but we follow the "spirit" of the Law, which is love.
Jesus too was talking about love, and not Law, when he said "Keep my commandments" (John 14:15). In John 15:10 he said again, "If you obey my commands, you will remain in my love,"--and then in verse 12 and again in verse 17 he tells us what "commands" he means: "This is my commandment, That you love one another, as I have loved you."
So do Christians keep the Ten Commandments? Not in the literal (letter of the Law) sense. Most of us don?t worship on Saturday, the Jewish Sabbath (Hebrews 4 says the Sabbath for us is symbolic of our rest in God through Jesus Christ). But we keep the spirit of the Ten Commandments, which is love.
We?re not under the Law. Then why do we quote the Law? Because a lot of things in the Law are still true. Love God and your neighbor is still true. Homosexuality is still an abomination, because it goes against nature, against the way we were made.
But the Law itself is not for us today to live by. It was given to the people under the Old Covenant to teach the lesson that trying to do good on our own, just from being told what to do, is insufficient. We need God working in us through the Spirit. It?s true that under the Old Covenant God was also saving people because of their faith, just as he does today. The difference is that for them the nature of grace (salvation by faith through Jesus Christ) was not fully revealed; it is only to us New Covenant believers that grace has been fully revealed.