Paul is laying down the basics of salvation. Faith alone, not by works. Salvation is believing in Jesus Christ, not by being a good person. The world seems to have this good deeds vs bad as the judge for salvation. Here Paul says obedience to the law will not save you but only faith in Christ saves you. I am glad that I am not judged by my deeds as I am a sinner and know the depths of my own sin. The law makes it clear to me that I have no chance of keeping the law and am desperate need of saving. Thank you God for faith.