Three words, all having different meetings, but have a place in the church. Let's start with Justice. The word means administrating a standard of correctness. Simply put administrating the penalty for a wrong doing. If you get caught for speeding, the just thing for the officer to do is to give you a ticket. That is what you deserve for breaking the law.
You hope the officer will walk up to you and say, "I am going to just give you a warning." He is forgiving you for speeding with a warning. That is Mercy. Mercy is defined as "compassion shown to an offender." If an officer gives you a warning he is showing compassion--Mercy.
Let's say you really break the law. You have to go before the judge and he sentences you to a huge fine, jail time, community service and loss of your license. You hear the verdict and know there is no way you can pay it because the burden is to large for you to handle. Before you are taken away the judge says wait a minute. My son has decided to pay your penalty for you. He will pay the fine, take the jail time, do the community service and his license will be suspended. The judge looks at you and says, "Your penalty has been paid in full."
That is grace. That is what Jesus did for you. You deserve hell, separation from God for all eternity, but Jesus paid that penalty for you in full. All you have to do is decide if you are going to accept his grace, let him pay your penalty or you decide to pay the penalty yourself. Not even a question is it? You let him pay your penalty.
So how does Justice, Mercy and Grace translate into our everyday lives in the church and as Christ followers. First, we need to be slow to levy justice. There is a time for justice. When evil needs to be purged from the church or someone is boldly sinning and damaging God's kingdom. Then Justice needs to be practiced. Paul says in 1 Corinthians 5 to kick that person out of the church and to not even eat with them so that on the day of the Lord they may be saved.
Mercy is practiced when we forgive someone. They admit they have done wrong and have decided to change their path. They are willing to accept their penalty, but instead you forgive. You show mercy and give them a warning.
Then Grace is when we go out of our way to love someone who does not deserve it. Showing grace is when a follower of Jesus just goes beyond what is normal and serves someone who has not earned the right to be served. That is what Jesus did for us. We don't deserve grace yet he paid our penalty for sin anyway. There are times we extend grace to people who don't serve it. They may need to see grace in a very practical so they may come to know Jesus.
Here is a truth about Grace, Mercy and Justice. Most of the time Christians are quick to want mercy and justice for themselves, but want judgment for someone else. Christians are also quick to say to other Christians who try to hold them accountable, "You are not acting like Jesus. You are judging me rather than showing grace and mercy." Look at Jesus' life. He did both. He served up justice when it was needed and mercy when it made sense. He showed us all grace by what he did on the cross. The righteous died for the unrighteous.