Romans 4:5, And to the one who does not work but believes in Him who justifies the ungodly, his faith is counted as righteousness.
Justification by faith is the principal doctrine of Christianity, and which sets it apart from all other religions; for it is only in Christianity that says you are saved by the grace of God via the means of faith, i.e. believing God (Ephesians 2:8-9).
What is God’s grace? It is His favour (חֶסֶד, χάρις). If you are in someone’s favour, this means you receive nothing but goodwill from them. Being in God’s favour, then, is to receive nothing but His goodwill, which is His pronouncing you free from your guilt of sin. How does He deliver this justification to you? He gives you faith when you hear His Word (Romans 10:14-15). When you hear His Word, He is offering you faith. If you push away the Holy Spirit—as is our natural condition—you accept your condemnation.
What makes Christianity so special? It is the only religion that proclaims God’s grace toward you, whereas all others demand you rely on your fickle, feeble human will.
The Lutheran Column 