Galatians 2:16, Yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified.
The falsity of works righteousness could not be more palpable. So, what use are good works? I must borrow from the wisdom of Luther again: “We must do good works, but our confidence must not be built on them, but on Christ’s work. We should not attack sin, death, and hell with our works, but send them away from us to the righteous Saviour, to the King of Zion, who rides on the donkey. He knows how to treat sin, death, and hell: He kills sin, chokes death, and devours hell. Let man take care of such matters, and apply your works to your neighbour, so that you have a sure testimony of faith in the Saviour who kills death” (from the Church Postil, sermon for Pentecost on Acts 2:1-13, Luther’s Works 77:329). Thus, our works coram Deo (before God) are worthless, but our works coram mundo (before the world) are good, for it is our neighbour who needs such good works. When we are judged by our works, no matter how “good” they are, we are condemned. But when we are judged by faith in Christ—by Christ’s works—God justifies us and thus deems us blameless before Him for the sake of Christ alone.
The Lutheran Column 