Sin can be defined as not keeping God’s law. But let’s tie this definition in with another definition of sin–“for whatsoever is not of faith is sin.”
Sin can be defined as not having faith. Thus, sin is defined as not keeping the law, which is the same thing as not having faith.
“Do we then make void the law through faith? God forbid: yea, we establish the law.”
Keeping the law and having faith work to the same end–doing what God says, doing righteousness. “not having mine own righteousness, which is of the law, but that which is through the faith of Christ.”
What the law could not do, faith does by the Spirit who fulfills in us the righteousness of the law.
Law and faith are opposite approaches to the same thing–righteousness. The Law has the End, but cannot provide the Means. But this doesn’t mean the law is evil, but rather we are! That’s why God requires faith, which produces in us what the law requires, but cannot fulfill.
“I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain.”