Abraham believed God, and it was credited to him as righteousness. Now to the one who works, wages are not credited as a gift but as an obligation. However, to the one who does not work but trusts God who justifies the ungodly, their faith is credited as righteousness. David says the same thing when he speaks of the blessedness of the one to whom God credits righteousness apart from works:What fits for Abraham, fits for Christians.Blessed are those whose transgressions are forgiven, whose sins are covered. Blessed is the one whose sin the Lord will never count against them. (Romans 4:3-8) [Hat tip to boatbums]
Catholics may do works for salvation, but plain everyday born again Christians will do works, but not for salvation. We only need to be saved once, and it's forever. Jesus said so.
But that's not so. Nobody thinks that works w/out faith are anything but atheist humanism, which even multiplied x 10,000 don't add up to our eternal salvation.