From: Matthew 5:20-26
Jesus and His Teaching, the Fulfillment of the Law (Continuation)
(Jesus said to His disciples,)  "For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the Kingdom of Heaven.
 "You have heard that it was said to the men of old, `You shall not kill; and whoever kills shall be liable to judgment.'  But I say to you that every one who is angry with his brother shall be liable to judgment; whoever insults his brother shall be liable to the council, and whoever says, `You fool!' shall be liable to the hell of fire.  So if you are offering your gift at the altar, and there remember that your brother has something against you,  leave your gift there before the altar and go; first to be reconciled to your brother, and then come and offer your gift.  Make friends 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 till you have paid the last penny.
20. "Righteousness": see the note on Matthew 5:6 (see below). This verse clarifies the meaning of the preceding verses. The scribes and Pharisees had distorted the spirit of the Law, putting the whole emphasis on its external, ritual observance. For them exact and hyper-detailed but external fulfillment of the precepts of the Law was a guarantee of a person's salvation: "If I fulfill this I am righteous, I am holy and God is duty bound to save me." For someone with this approach to sanctification it is really not God who saves: man saves himself through external works of the Law. That this approach is quite mistaken is obvious from what Christ says here; in effect what He is saying is: to enter the Kingdom of God the notion of righteousness or salvation developed by the scribes and Pharisees must be rejected. In other words, justification or sanctification is a grace from God; man's role is one of cooperating with that grace by being faithful to it. Elsewhere Jesus gives the same teaching in an even clearer way (cf. Luke 18:9-14, the parable of the Pharisee and the tax collector). It was also the origin of one of St. Paul's great battles with the"Judaizers" (see Galatians 3 and Romans 2-5).
21. Verses 21-26 gives us a concrete example of the way that Jesus Christ brought the Law of Moses to its fulfillment, by explaining the deeper meaning of the commandments of that Law.
22. By speaking in the first person ("but I say to you") Jesus shows that His authority is above that of Moses and the prophets; that is to say, He has divine authority. No mere man could claim such authority.
"Insults": practically all translations of this passage transcribe the original Aramaic word, "raca" (cf. RSV note below). It is not an easy word to translate. It means "foolish, stupid, crazy". The Jews used it to indicate utter contempt; often, instead of verbal abuse they would show their feelings by spitting on the ground.
"Fool" translates an ever stronger term of abuse than "raca"--implying that a person has lost all moral and religious sense, to the point of apostasy.
In this passage our Lord points to three faults which we commit against charity, moving from internal irritation to showing total contempt. St. Augustine comments that three degrees of faults and punishments are to be noted. The first is the fault of feeling angry; to this corresponds the punishment of "judgment". The second is that of passing an insulting remark, which merits the punishment of "the council". The third arises when anger quite blinds us: this is punished by "the hell of fire" (cf. "De Serm. Dom. in Monte", II, 9).
"The hell of fire": literally, "Gehenna of fire", meaning, in the Jewish language of the time, eternal punishment.
This shows the gravity of external sins against charity--gossip, backbiting, calumny, etc. However, we should remember that these sins stem from the heart; our Lord focuses our attention, first, on internal sins--resentment, hatred, etc.--to make us realize that that is where the root lies and that it is important to nip anger in the bud.
23-24. Here our Lord deals with certain Jewish practices of His time, and in doing so gives us perennial moral teaching of the highest order. Christians, of course, do not follow these Jewish ritual practices; to keep our Lord's commandment we have ways and means given us by Christ Himself. Specifically, in the New and definitive Covenant founded by Christ, being reconciled involves going to the Sacrament of Penance. In this Sacrament the faithful "obtain pardon from God's mercy for the offense committed against Him, and are, at the same time, reconciled with the Church which they have wounded by their sins" ("Lumen Gentium", 11).
In the New Testament, the greatest of all offerings is the Eucharist. Although one has a duty to go to Mass on Sundays and Holy Days of Obligation, an essential condition before receiving Holy Communion is that one be in the state of grace.
It is not our Lord's intention here to give love of neighbor priority over love of God. There is an order of charity: "You shall love the Lord your God with all your heart, with all your soul and with all your strength. This is the great and first commandment" (Matthew 22:37-38). Love of one's neighbor, which is the second commandment in order of importance (cf. Matthew 22:39), derives its meaning from the first. Brotherhood without parenthood is inconceivable. An offense against charity is, above all, an offense against God.
[Note on Matthew 5:6 states:
6. The notion of righteousness (or justice) in Holy Scripture is an essentially religious one (cf. notes on Matthew 1:19 and 3:15; Romans 1:17; 1:18-32; 3:21-22 and 24). A righteous person is one who sincerely strives to do the Will of God, which is discovered in the commandments, in one's duties of state in life and through one's life of prayer. Thus, righteousness, in the language of the Bible, is the same as what nowadays is usually called "holiness" (1 John 2:29; 3:7-10; Revelations 22:11; Genesis 15:6; Deuteronomy 9:4).]
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.