"Therefore, if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there in front of the altar. First go and be reconciled to your brother; then come and offer your gift.”
This passage speaks of the relationship with a brother. Jesus is talking about fellow-believers in the faith. It could mean fellow Jews as the blood line, but, spiritually, kingdom- people go beyond blood relationship. Since the cross, we are family in Christ with one another. When the relationship has been broken it needs to be made right, not only with God but with others who may be affected.
Jesus taught when you go to give a gift, if your brother has something against you go and make it right. His listeners practiced temple worship with animal sacrifices. When you are at worship seeking the face of the Lord, you should seek reconciliation. It is hard to ask God to forgive us our sins, when we are not willing to forgive the sin of those who have sinned against us or if we have sinned against someone. The call for sincere worship, both in our relationship with God and in our relationship with our fellow brothers, is to make it right.
Scripture reveals the bitter pain that unresolved anger can have. It breeds and grows. It begins with one person who feels offended by another. Perhaps it was just a lack of communication or a misunderstanding.
Matthew 18 Jesus speaks of church discipline and reconciliation. If another has done something wrong it is for you to go to him, meaning you should take the initiative to try to reconcile. If you have offended someone or if you have been wronged, go and make things right. Many times, the other person may not be aware that he has wronged you or that he might have been offended by something you said or did.
Tensions between people easily breed between tensions between families, which breed tensions between friends of family members and spreads to churches. More church splits are over hurt pride than over any serious doctrinal issues. More church fights are over personality conflicts and power. More church fights are over bruised egos and over the lack of guts to say, “We need to talk over our differences rather than ignore them.” Generally, when you've been hurt it's hard to forgive or seek forgiveness. It's so easy for Satan to show you reasons why you are right, and the other person is wrong. Satan makes it seem like we are always the innocent party, mistreated and maligned until revenge, bitterness, and grudges grow. We cannot fool God with what is in our hearts.
Twice I've been in a church service when before communion could continue one fellow went to another publicly and announced to the church body his wrong attitude toward a Christian brother in the church. He wanted to be cleansed by confessing it to God and to the person before the church, because it affected the church unity. It did wonders in their own Christian lives and also in the lives of the members. When parties seek reconciliation God can shower forth His blessings. God's Spirit works in marvelous ways.