Nothing but faith is needed to be saved, to give God the honor due Him and to accept Him as my God, confessing that He is just, true, and merciful. Such faith sets us free from sin and all evil. If I have thus given God his due, I live the rest of my life for the benefit of my neighbor, to serve and to help him. The greatest work that follows from faith is that with my mouth I confess Christ, sealing that confession with my blood and, if it is so to be, laying down my life for it. Not that God needs this work. But I am to do it that my faith may thereby be proved and known, that others may likewise be brought to believe. Then other works follow; they must all be directed toward serving my neighbor.
(What Luther Says, para 3020, page 960 - pointing out from I Peter 1:15-16 that since Christians have acquired perfect peace themselves, they can now devote their time to bringing it to others.)