Then what becomes of our boasting? It is excluded. By what kind of law? By a law of works? No, but by the law of faith. (ESV)
There is a consequence for those who would attempt to be made right with God by a law of works. Any success that could be gained in keeping even a small aspect of the law touches the prideful heart of man. Instead of giving God the glory for giving man the ability to do good man is likely to claim the glory for himself and boast about his efforts.
This boasting in the law of works is something that Jesus himself encountered when he walked this earth. Consider those who were the most "religious" in the land. The Pharisees, the teachers of the Law, were the worst when it comes to boasting in the law of works. Jesus described their boastful actions.
In Matthew 23:5 Jesus said this about the Pharisees: "They do all their deeds to be seen by others. For they make their phylacteries broad and their fringes long." Jesus recognized that their efforts to obey a law of works was so that they could be seen by others as being righteous. They wanted to boast about themselves. This is the natural result of a law of works.
Paul says that our boasting is to be excluded. How is it excluded? By a law of faith. Because of Jesus Christ fulfilling perfectly the Law of God for us, we are only able to be made righteous by placing our faith in Christ. This is the law of faith. And there is a natural consequence of the law of faith. It gives God the glory and eliminates our boasting.
What law are you living by? The law of works or the law of faith. It will be evident to all by whether you are living to boast in yourself or whether you are giving all the glory to God.