There are a lot of big words in the Bible. Some of them are names of cities or people groups that we are not familiar with. Others are more theological in nature and hold very significant meaning for us as Christians. Of all the big words found in the Bible perhaps the most significant one is justification.
Justification is a word that most of us have heard. Usually when we hear this word the definition is related to giving a reason for doing something. For example someone might ask you to give a justification for why you decided to not invite them to your party. Many times this is even seen as something akin to an excuse. That is not the definition that we use when we talk about the Christian doctrine of justification.
In the New Testament the Greek work for justify is δικαιόω. Mounce's Complete Expository Dictionary of Old and New Testament Words defines the word to mean "to declare righteous". Notice that the definition does not say that it means to "make righteous" but instead that it is declared to be so. This is an important part of the Protestant understanding of justification. We are not made righteous by anything that we do but instead we are declared to be righteous on account of the work of Jesus Christ.
The natural assumption of humans is that we earn our salvation by doing good works. This is essentially the default religion of the human heart. It can express itself in many ways but in our day I believe the most common way we see this expressed is the thought that good people go to heaven. How we define a "good person" is a sliding scale but usually means that the person is generally nice to people and doesn't cheat on their taxes. There is a sense where it is true that a "good person" would go to heaven but our human sliding scale is not what determines whether someone is good. The Bible is clear that there are none who are righteous, not even one. (Romans 3:20; Psalm 14:1-3; 53:1-3; Ecclesiastes 7:20) In other words, there is no one who has met God's righteous standard. Each and every one of us is a sinner and have fallen short of God's glory. (Romans 3:23) This is why we need something else other than our righteousness because ours is not going to cut it. Period.
That's why this idea of justification is so important. In the midst of our sin and misery God comes to us and because of what Jesus Christ has done for us we are declared righteous. We are not given a clean slate. We are not improved and now we can hope to do better. We are declared righteous. Why? Because our righteousness is now coming from somewhere outside of us. Christ's righteousness is now our righteousness.
Paul talks about this amazing good news in Romans 3:21-26. He says that a righteousness from God, apart from the law, has been made known. It is a righteousness from God and it comes through faith to those who believe. We are justified (declared righteous) by the grace of God. This word "justification" is vital in understanding the Christian faith. Jesus did not come only to be a moral example for us. He came to live for us in his perfect life. He came to die for us in his death on the cross. He rose again that we too may be raised on the last day. He ascended into heaven to intercede for us at the right hand of the Father. He did it all that we might be justified by having faith in what he has done for us. Instead of working to save ourselves by being a "good person" we instead give up our hopes of being seen as righteous on our own and fall at the feet of Christ. We trust in him, knowing that He alone has the power to save us.