It is essential to understand that Jesus did not do away with laws, but brought to completion the laws that already existed. Likewise, He did not do away with the Old Testament death penalty principles, which act as guides to civil governments. Jesus was a pioneer, not a revolutionary. A revolutionary seeks to destroy the existing order and places himself above conventional standards. A pioneer accepts the restraints laid upon him and moves forward.
Men's governments deal with the end of the act, Christ deals with the beginning. Jesus changed the law's restraint from the act to the motive. For the Christian, merely abstaining from the act is not sufficient. Jesus imposes the positive obligation of the spirit of the law on him. He seeks to prevent crimes of violence by rooting out the attitudes and drives in a person's character that make him kill. The New Covenant law searches the heart without doing away with the Old Covenant letter.
People can sometimes get infantile, sentimental feelings about Christ and fail to understand the practical realities of what He taught. A cursory reading of Matthew 5:21-22 shows that He is speaking not so much about murder but of the steps that lead to it. He traces the roots of murder and war to three major sources: 1) anger, 2) hatred, and 3) the spirit of competition and aggression—in short, the self-centeredness of passionate carnality.
"Angry without a cause" indicates someone vainly or uselessly incensed. It describes a person so proud, sensitive, or insecure that he gets angry about trifling things. He wears his feelings on his sleeve and is easily offended. He then broods on the offense and nurses it into a grudge.
What may make Jesus' comments even more startling is that many commentators feel that the best Greek manuscripts do not include "without a cause." If this is so, Jesus is saying that even getting angry—with or without a "justifiable" cause—puts one in danger of breaking this commandment! The Bible permits anger against sin (righteous indignation) but not anger against another person.
Raca literally means "vain fellow," someone who is deemed shallow, empty-headed, brainless, stupid. People said raca in a tone of voice that conveyed scorn, contempt, or bitterness born of pride, snobbery, and prejudice.
"You fool" implies a moral fool. One using it was casting aspersions upon another's character to destroy his reputation. It is an expression of condemnation, of character assassination.
We should not take the increasing severity of punishment in the examples Jesus gave literally. He is teaching about the sin of murder, and the punishment is the same in each example—death. He gives the gradations to teach the degree of wickedness and viciousness of each sin.
William Barclay, in his commentary on these verses, writes:
What Jesus is saying here is this: "In the old days men condemned murder; and truly murder is forever wrong. But I tell you that not only are a man's outward actions under judgment; his inmost thoughts are also under the scrutiny and the judgment of God. Long-lasting anger is bad; contemptuous speaking is worse, and the careless or malicious talk which destroys a man's good name is worst of all." The man who is the slave of anger, the man who speaks in the accent of contempt, the man who destroys another's good name, may never have committed a murder in action, but he is a murderer at heart.
Brooding anger, contempt, and character assassination are all the spirit of murder. Christ here traces murder to several of its major sources. To continue in any of these states breaks the sixth commandment. Death is the penalty. Christians have to keep the spirit of the law.