For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith. Romans 1:17
"Luther was looking now at the Greek word that was in the New Testament, not the Latin word. 
The word dikaios, dikaiosune, which didn’t mean to make righteous, but rather to regard as righteous, to count as righteous, to declare
as righteous.
And this was the moment of awakening for Luther.
It’s what he called a justitia alienum, an alien righteousness; a righteousness that belongs properly to somebody else. It’s a righteousness that is extra nos,
outside of us.
Namely, the righteousness of Christ.
And Luther said,
“When I discovered that, I was born again of the Holy Ghost. And the
doors of paradise swung open, and I walked through.” NathanBingham