Obedience is really about reconciliation. The place of the Law in the context of the Christian life is an integral one, but a tricky one. One of my chief concerns in teaching on obedience and the Law is that order be kept straight. We see it in the Exodus story, and we see it in the order of salvation. We are set free to then follow. God did not hand Moses the Law before the burning bush. He did not deliver the Law to the Israelites while they were still in bondage. He delivered them into the wilderness first.
I think that's really important. We are set free to follow. The call and the deliverance precedes obedience in the same way that a changed heart precedes changed behavior. (Tim Keller is the best of the best on this subject from a pastoral perspective.)
But it still leaves the command to obey, the command to follow the Law, sitting heavy on us like a weight. And so my aim is to give it context, to put the Law in its proper framework, and for post-cross Christians the context and framework is the same as it was for post-Exodus Israelites. Or at least should be. Love.
God gave the Law out of love. And when the Pharisees tried to trick Jesus into a legal fumble, it was love that Jesus used to frame the Law:
The greatest commandment is to love the Lord your God with all your heart, soul, mind and strength, and to love your neighbor as yourself.
There are the two tables of the Law divinely summed up (as the first four commandments are about our relationship with God and the last six commandments are about our relationship with our neighbor) and placed not in the context of burden or duty or even creating a peaceful civil society. They are about love creating a community of reconciliation.
Because the Law addresses the Fall. The two tables (God/neighbor) respond to the two divisions in the Fall -- sin brings separation from God and enmity between neighbors. The Law cannot "fix" this division, but it tells us how a people delivered by the love of God into the love of God ought to live the love of God as a living picture of reconciliation. (Paul's stuff in 2 Corinthians 5 about the message and ministry of reconciliation in relation to obedience is really helpful here.)
A community of reconciliation. That's the purpose of following the Law, just as its the purpose of following the "new" Law in the Sermon on the Mount. It's not about scoring points with God or getting qualified for salvation. It's about testifying to the reconciliation Christ's atoning work has accomplished by becoming a living picture of that reconciliation.
So I obey God's commands, then, not because I think it's good for society or because it inspires others to be nicer (a sort of karmic, "I'll scratch your back, you scratch mine" kind of thing) or even merely because "God said so" (although that's the hinge upon which worshipful obedience really turns). No, I obey God's command to honor my parents and not to lie, steal, murder, have sex with someone other than my wife, and covet because I love my parents and my neighbor, and even though we all deserve to have the worst done to us, it is ultimately an act of grace (again, when committed to out of love) to give them the best of myself. By obeying God's command to live rightly, I am demonstrating to others the grace I've been given and I am extending it beyond myself to others.
And that's how obedience is ideally about reconciliation.