Paul makes another contrast. What avails a person is faith working through love. These three verses are important because they introduce "Spirit" and that "faith works through love." Faith works. It works through - meaning "by means of" - love. In other words, if a person really has faith in the right things and the right Person, he will produce what? Love!
What is the Bible definition of love? "For this is the love of God, that we keep His commandments" (I John 5:3). That is beautiful! Similarly, Paul is saying that, if we really believe in the right things and the right Person (that is, have faith), then it will produce the keeping of the commandments.
The evidence of our faith, then, is in whether or not we keep His commandments. John tells us that the basis of love is commandment-keeping. It is not the whole picture, because emotion, feeling, is also tied to it, but we have to begin somewhere, and the bottom line is keeping the commandments.
Another statement that proves that Paul was not doing away with law keeping comes right from this context. The word "Spirit" reflects on a subject he dealt with earlier. The enemy - Judaistic Gnostics - believed that their calling and election by God came because they had the law and kept it. But Paul is saying, "No. We are drawn to God by His Spirit," which is what Jesus says in John 6:44.
Also, truth is revealed by God's Spirit (I Corinthians 2:10-16; John 14:17; 15:26; 16:13), so our calling has nothing to do with our works. Romans 9:16 tells us that it is not of him who wills or of him who runs, but of God who shows mercy. Thus, we are in this position because God, by His Spirit, has drawn us. He, by His Spirit, has revealed Himself, His Word, and the purpose of life to us. Our calling and election are completely a work of grace. At the point of our calling, law-keeping has nothing to do with it, but comes into play later when our faith works through love.