From this it further follows, when a Christian does good works and shows love to his neighbor, that he does not thereby become a Christian or pious, but before this is done he must have been a Christian and pious. He indeed does good works, but his good works do not make him a Christian. The tree brings or yields good fruit, but the fruit does not make the tree good. So also here, no one becomes a Christian through his works, but through Christ.
– Martin Luther –