What does the New Testament say about killing?

As to the two commandments He quoted, His teaching evidently is that God has respect not only to the overt act but also to the inward disposition of the heart. What is prohibited is not merely the act of murder or adultery but the hatred and the lust of which the act is the expression. Judged by this standard, who is going to stand before the holy demands of Sinai? The "righteousness" of the scribe and Pharisee utterly collapses. Yet in both cases, having exposed this fact, He added some further instruction.

Now He takes up the law in its various parts, at least what has to do with men. Here He does not enter into what touches God directly, but first of all takes up that which flows from human violence, and after this the great flagrant example of human corruption; for violence and corruption are the two outstanding forms of human iniquity. Before the flood even, such was the condition of men: "The earth was corrupt before God, and the earth was filled with violence." Here, in verse 21, we have the light of the kingdom cast on the command, "Thou shalt not kill: and whosoever shall kill shall be in danger of the judgment." The law took cognizance of this extreme form of violence; but our Lord gives length, breadth, height, and depth to it: "But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire" (ver. 22). That is, our Lord treats as now coming under the same category with murder, in the sight of God, every kind of violence, and feeling, and expression; anything of contempt and hatred, whatever expresses the ill-feeling of the heart; any putting down of another, the will to annihilate others as far as character or influence is concerned: all this is no better than murder in God's searching eye. He is expanding the law; He is showing now One who looks at and judges the feeling of the heart. Therefore it is not at all a question merely of the consequences of violence to a man, for there might be no very bad effect produced by these words of anger, but they proved the state of the heart; and this is what the Lord is dealing with here. "Therefore if thou bring thy gift to the altar, and there rememberest that thy brother hath aught against thee, leave there thy gift before the altar, and go thy way: first be reconciled to thy brother, and then come and offer thy gift" (vers. 23, 24). He is not yet manifesting the Christian in his entire separation from the Jewish system. These words clearly show a connection with Israel — though the principle applies to a Christian; for the altar has no reference to the Lord's table.

He takes some of the commandments which He wrote on the second table of stone and begins with the commandment: "Thou shalt not kill." Murder was the first awful fruit after the fall, sprung as it was from envy in the heart. The penalty of murder is the judgment. This, then, is the letter of the law. It dealt with the outward deed, but the heart itself it did not touch. Now He speaks. "I say unto you, that every one that is _lightly angry with his brother shall be subject to the judgment." (The word "lightly" belongs in here. It was dropped in some manuscripts, but stands in the oldest. It is not angry alone outwardly, but even the remotest feeling of displeasure is meant.) It shall be as if he had committed the deed "thou shalt not kill." Every one that hates his brother is a murderer (1 John 3:15). "Whosoever shall say to his brother, Raca (a word embodying hatred and contempt) shall be called before the Sanhedrin; but whosoever shall say, Fool, shall be subject to the penalty of the hell fire." It will be so, no doubt, when the kingdom will be come into the earth; swift judgment will overtake the offender. But the words lay bare the heart and show the impossibility of man to stand before God, who judges the heart, in their own righteousness. The believer being the partaker of the divine nature, is righteous and loves his brother. Only the reception of eternal life, which is Christ Himself, can produce righteousness and love. "Whosoever has been begotten of God does not practice sin, because His seed abides in him and he cannot sin, because he has been begotten of God. In this are manifest the children of God and the children of the devil. Whoever does not practice righteousness is not of God, and he who does not love his brother" (1 John 3:9-11). The believer walking in the Spirit will in no way fulfill flesh's lust.

He next puts the case even more strongly. "Every one that hateth his brother is a murderer." There he comes down with greater severity. It is not merely one that does not love, but the positive activity of hating. More outspoken in word and outrageous in conduct, he betrays his hatred, and is called a "murderer." The apostle here goes down to the root of things. As hatred is found to mark his spirit when tried, he is a murderer in principle; just as the Lord pronounces a man to be an adulterer in principle who indulged in lust which he ought not to allow, but to judge and be ashamed and humbled for it. God deals with the heart and not the externals only in Christianity. It is the inward working, as well as what comes out, which stamps the professor, however inadmissible and impossible in a court of law. "And ye know that no murderer hath eternal life abiding in him." It is the very opposite of Christ, and the closest correspondence with the devil. For what can be more like our adversary, the liar and murderer from the beginning?

Verse 15 puts the case even more strongly. The fact is that in this matter we cannot be neutral. If we do not love our brother we hate him; and he who hates is potentially a murderer. Cain was an actual murderer, but in Matthew 5:21-22 the Lord Jesus lays the emphasis not on the act but on the anger and hatred which prompted the act, and so does our scripture here. He who is possessed with a spirit of hatred is possessed with the spirit of murder, and no such person can be possessed of eternal life. As we have seen, eternal life is ours as continuing or abiding "in the Son and in the Father" (1 John 2:24-25). Abiding in Him, eternal life abides in us, and the essential nature of that life is love.

“Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.” Hatred is the very spirit of murder. The apostle of course speaks of the man’s nature here, not of his acts, though the hateful nature of Cain issued in his actual murder of Abel. The antichrist will at first be apparently very friendly with the believing remnant of Israel, his words “smoother than butter,” but “war was in his heart;” so that callous persecution will take the place of his smooth words. The hatred of Judas did not actually expose itself for three and a half years, but then he was proven a murderer also. Dreadful designation of all who use a form of godliness as a cloak of deception!

“Ye know that no murderer hath eternal life abiding in him ” has often been misunderstood. It has been taken to mean that no murderer can be saved. Let us seek to understand what the apostle says. In the first place, he declares that “whosoever hates his brother is a murderer.” Is it not plain that the apostle points to the nature which characterizes one who, like Cain, is of the wicked one? Thus a man does not need to take the life of a fellow-man to be a murderer; he is that by the very fact that he possesses that nature. In this sense all men are murderers by their very nature since the fall. But when the grace of God lays hold of one who is such in the eyes of God, he is born anew, “born from above. ” He possesses a new nature, which now characterizes him in God's eyes. God looks upon him as having passed out of death into life. He no more looks at him according to the old nature which is still in him, but according to what he is as born of God. A new life dwells in him. It is in the character of this new life that God now views him. (C. Crain, Readings on Romans)

"Ye know that no murderer hath eternal life abiding in him" has often been misunderstood. It has been taken to mean that no murderer can be saved. Let us seek to understand what the apostle says. In the first place, he declares that "whosoever hates his brother is a murderer." Is it not plain that the apostle points to the nature which characterizes one who, like Cain, is of the wicked one? Thus a man does not need to take the life of a fellowman to be a murderer; he is that by the very fact that he possesses that nature. In this sense all men are murderers by their very nature since the fall. But when the grace of God lays hold of one who is such in the eyes of God, he is born anew, "born from above." He possesses a new nature, which now characterizes him in God's eyes. God looks upon him as having passed out of death into life. He no more looks at him according to the old nature which is still in him, but according to what he is as born of God. A new life dwells in him. It is in the character of this new life that God now views him.

Cain was a murderer, and the murderous hatred of his brother was in his heart before he actually slew him. So it was with the leaders of Israel who, with wicked hands, crucified and slew the Son of God. Jesus convicted them of their hatred to Him before they actually slew Him. Every one with hatred in his heart towards a Christian, because he is a Christian, is viewed by God as a murderer. God can and does look into the heart, and judges the motives and feelings of the heart; and where there is the hatred of the one who manifests the divine life, God calls it murder.

The sixth commandment: "Thou shalt not kill"

The Lord Jesus begins the first of the six examples with the words, "Ye have heard that it was said to the ancients" (A.V.-"them of old time"). The "ancients" here are not only the contemporaries of Moses, since the following text contains an addition to the original commandment. The audience of the Lord Jesus had heard two things: First, that the commandment, "Thou shalt not kill," was given by God, and second, what they knew had probably been added by the scribes since the Babylonian captivity, "and whosoever shall kill shall be in danger of the judgment." It would seem that "judgment" here means the judges and officers mentioned for example in Deuteronomy 16: 18 who were to be appointed in every town in Israel.