You have heard that it has been said by them of old time that you shall not kill, and whoever shall kill shall be in danger of the judgment of God. But I say unto you that whoever is angry with his brother shall be in danger of his judgment. And whoever shall say to his brother, Raca, or Rabcha, shall be in danger of the council. And whoever shall say to his brother, You fool, shall be in danger of hellfire.
Therefore, if you shall come unto me, or shall desire to come unto me, or if you bring your gift to the altar and there remember that your brother has anything against you, leave there your gift before the altar, and go your way unto your brother, and first be reconciled to your brother, and then come and offer your gift.
Agree with your adversary quickly while you are in the way with him, lest at any time your adversary deliver you to the judge, and the judge deliver you to the officer, and you should be cast into prison. Truly I say unto you, you shall by no means come out from there until you have paid the utmost farthing. (Matthew 5:21-26)
A more modern translation of the verses in the third part is as follows:
Accept accountability for your misconduct the instant it's brought to your attention, to avoid leaving this life unrepentant and risking condemnation. I warn you: You'll discover no way to escape before paying fully for every sin; and while in prison under condemnation, are you able to redeem yourself? I warn you that you cannot.
Who is the adversary in the third verse? It is your brother or sister who has something against you in the second verses. Remember, Christ's Law is a rule of community. What makes us think we'd be happy to live His law in Heaven if we don't first live it while here on earth?
Christ speaks about going to your brother who has something against you. In doing so I believe Christ is specifically making mention to the members of His Church rather than the world at large. Otherwise, he would have used the word neighbor.
And while he yet talked to the people, behold, his mother and brethren stood without, desiring to speak with him. Then one said unto him, Behold, your mother and your brethren stand without, desiring to speak with you. But he answered and said unto the man that told him, Who is my mother? And who are my brethren? And he stretched forth his hand toward his disciples and said, Behold my mother and my brethren. And he gave them charge concerning her, saying, I go my way, for my Father has sent me, and whoever shall do the will of my Father who is in Heaven, the same is my brother, and sister, and mother. (Matthew 12:46-50, see also Mark 3:31-35)
If you lived in the day of Nero the Roman Emperor who made being a Christian a crime punishable by death. He was not their brother. Therefore, they had no obligation to go and seek to reconcile with him.
Christ's Law is a rule of community. The members of this community are the members of His church. Each of us must come unto Jesus Christ or we cannot be saved. How do we do this? By faith, repentance, and baptism which brings the holy ghost to show us all things we must know.
Those who repent and come unto Him are His church. Any who declare more or less than this are not of Christ but are against him and are therefore not of His church.
Strong words but they are true and they are how Jesus Christ defines His church.