Justification is the act of declaring righteous. To justify yourself is to say (and believe) "I'm good or I'm right". For someone else to justify you is for them to say "you're good".
The Bible teaches that God justifies the ungodly. So that means he has made us, who are sinners, perfectly right in every way. He has done that through the sinless blood of Jesus in his role as our priest and mediator. When he rose from the grave, this act was complete never to be overturned or doubted. Rom 4:25, Heb 10:18.
Justification by Faith is the act of the born-again sinner when he turns to the Lord and believes in him. This is the sinner understanding what Jesus did and that God is satisfied with the sacrifice of Jesus. Having put his own trust in Jesus, he can say "I'm good. I've been made righteous in the eyes of God because I belong to Jesus." He then rests from worrying about his eternal life. Rom 5:1. JUSTIFICATION BY FAITH IS NOT THE SINNER LOOKING AT HIS OWN FAITH OR PROFESSION AND DRAWING THE CONCLUSION BASED ON THAT EVIDENCE THAT HE BELONGS TO JESUS. That would be justification by works and is meant for other people to know that you're born again; it doesn't work real well for oneself. Justification by Faith is not based on evidence that the sinner sees in himself that he's elect. Maybe this goes into it, but I believe what's really going on in Justification by Faith is the personal testimony of the Holy Spirit testifying directly to the heart that he is a child of God and not imputing his sin to him. Rom 8:16, Rom 4:8. The Holy Spirit is present as soon as the sinner is born again, but under the sound of the gospel there is a blessing that God gives in not imputing one's sins to them. This experience does not make the Justification in the eyes of God, but in the eyes of the sinner. This hope is not based on evidence the sinner sees in himself but in the love shed abroad in his heart by God. Rom 5:5. I believe this may happen several times over and I often need it again since from time to time I may forget I was purged from my old sins. David sought for this when he was convicted of his sins well after he was made to hope on his mother's breast.
Finally, Justification by Works is the act of other people looking at you and saying "he's good. Or he's been made righteous by the blood of Jesus and the quickening of the Spirit." This is by works because Jesus said by their fruits ye shall know them. We can't look into your heart, or feel the Spirit directly testifying to us of your new life. I read an influential Primitive Baptist preacher say that Justification by Works is proving to others that your belief is genuine. But that's not what justification means. It's proving that you're righteous, not that you believe. Yes, if you make a profession of Jesus, your works either agree with that profession or cast doubt on it, but that's not what Justification by Works really is. What fruit proves that you're good? The fruit of the Spirit proves that the Spirit has born you again: Love, joy, peace, longsuffering, gentleness, goodness, faith, meekness, temperance. So yes, belief requires faith which provides justification, but when we're talking about justification by works there is no need to privilege faith over any of the fruit of the Spirit. Just because you cannot see someone's faith, doesn't mean you can't know they're born of God if you can see other fruit of the Spirit.
