The Gospel according to Matthew has a passage, Matthew 18:15-17, which some consider to be a form of church discipline, but which I think can be understood as a church dispute resolution process in three steps.
Step One: Matthew 18:15 “If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother.”
Step Two: Matthew 18:16 “But if he does not listen, take one or two others along with you, that every charge may be established by the evidence of two or three witnesses.”
Step Three: Matthew 18:17 “If he refuses to listen to them, tell it to the church. And if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector.”
Step One: One of the first principles of dispute resolution is direct communication. When your brother or sister sins against you, first talk with them directly in private. Unfortunately What happens in churches, what happens everywhere, is people triangulate. They begin by talking to others about how this person did this or that, but that only makes the problem worse. If you’re upset with someone, talk to them directly in private. And when you do that, try to separate the person from the problem. In dispute resolution people are not the problem; the problem is the problem, and the question is how do you solve that problem.
Step Two: If, after listening to you, the matter involving your sister or brother is not resolved, invite one or two other church members to join you and speak with this person again.
Step Three: Interpreted literally, this last verse has led to the practice of shunning, the expelling of members from the church community.
But when you read Matthew 18:15-17 in context, one notes that this short passage is framed by two other longer passages, which call for forgiveness and reconciliation. Matthew 18:10-14, which precedes this passage, tells a story about a shepherd with a 100 sheep. When one sheep goes missing, the shepherd leaves the other 99 to search for lost sheep, and then upon finding the lost sheep, the shepherd rejoices. In Matthew 18:21-22, which follows the three steps, Peter asks Jesus how many times should he forgive a member of the church who sins against him…”seven times?” And Jesus answers, “Not seven times, but I tell you, seventy-seven times.”
If this doesn’t convince you, consider the story in Luke 19:1-10, when Jesus visits Jericho, and encounters Zacchaeus, the town’s tax collector, who’s so short he has had to climb a sycamore tree to see Jesus. When Jesus sees him up in the tree, he tells Zacchaeus to climb down and then invites himself to Zacchaeus’ house, much to the dismay of others. Jesus’s spontaneous invitation prompts this tax collector to give half of his possessions to the poor and promise to make amends to anyone he has ever cheated. Instead of shunning this tax collector, Jesus embraced him and changed Zacchaeus’ life.
Finally, regarding how Christians should treat Gentiles, consider the story in Acts in which Peter baptizes Cornelius, the God-fearing Roman Centurion, in Caesarea, and then reports back to the Church in Jerusalem that “God has given even to the Gentiles the repentance that leads to life.” Acts 11:18.