In chapter 3 of Galatians, Paul continues his defense of living by faith as opposed to living by the law.  God initiates and provides The Way to salvation.  Why do we so readily go back to trying to earn it by keeping the law.  Paul quotes the Old Testament saying that  "Abraham believed God and God counted him as righteous because of his faith."  The law was given for a purpose between the promise and the fulfillment of that promise, but now that the promise has been fulfilled there is a "new and better way," and we are not turning back.