Matthew 5:25-26
Come to terms quickly with your accuser while you are going with him to court, lest your accuser hand you over to the judge and the judge to the guard, and you be put in prison. Truly I say to you, you will never get out until you pay the last penny
The selfish anger that Jesus attacks in this section of the sermon on the mount can drive a wedge between people. Christians will hurt each other, we will get offended and cause offense - that is guaranteed due to the remaining sin in our lives. However churches should be full of people who are seeking reconciliation when those things happen. Instead, churches are too often full of people holding onto grudges against their brothers and sisters or being more willing to stop attending church than attempt reconciliation. We, enemies of God, have been reconciled to God through Jesus death on the cross, should be seeking reconciliation with others. We, who have been shown mercy, should be showing mercy to others.
Jesus says our righteousness must exceed that of the scribes and Pharisees. They were pleased that they didn't murder. We can not be satisfied that we managed to not hit/slap/bite/shout but repentant for the anger/contempt/passive aggressiveness that is in our heart and cry out to God for mercy.