This is the seventh post on Christian ethics in my ongoing series, theology in bullet points. The first unit in this series had to do with God and Creation (book here), and the second unit was on Christology and Atonement.
We are now in the third and final unit: The Holy Spirit and the Church. The first set of posts in this final unit was on the Holy Spirit. The second set was on the Church. The third set was on sacraments. This final section is on Christian ethics.
You shall not murder.
1. Most cultures throughout time have considered it wrong to kill an innocent person who is an equal in your group for no reason. Of course many cultures have no problem with killing people from other groups, and at times a culture might allow someone to kill an inferior in a group. But the general prohibition against murdering innocent people holds generally for all humanity throughout time. 
Within Israel, it was the same: "You shall not murder" (Exod. 20:13). It was not permissible to kill anyone within the boundaries of Israel for no cause. Certainly this was true of other Israelite males. We can infer that it was true of killing Israelite women. Even the stranger in the land was protected.
2. The Law of Israel distinguished between intentional murder and unintentionally causing the death of someone or, just perhaps, killing someone in self-defense. The key element here are the cities of refuge that were set up within Israel. These were cities to which someone might flee if s/he accidentally caused the death of someone.
Deuteronomy 19 gives a good picture of the cities of refuge (see also Num. 35; Josh 20). It is clear that an intentional murderer will find no refuge in those cities. Such a person will be handed over to the family of the one murdered and put to death (Deut. 19:11-13). Rather, they were for the person who unintentionally causes death. Deuteronomy gives the example of someone who, while swinging an ax, might accidentally strike another person with the ax-head.
In more than one place, such an individual is described in this way: "the two had not been at enmity before" (Deut. 19:4; Num. 35:23; Josh. 20:5). Presumably killing someone in self-defense was considered justified, for Exodus 22:2 does not consider someone guilty for killing a robber in your house after dark. Nevertheless, shedding of blood was taken very, very seriously in the holiness codes of the Law: "You shall not pollute the land in which you live; for blood pollutes the land, and no expiation can be made for the land, for the blood that is shed in it, except by the blood of the one who shed it" (Num. 35:33). Deuteronomy even says not to show mercy on a murderer (Deut. 19:13).
3. Of course in the New Testament, believers found themselves in a different social system. They were not in control of civil law, and the Jews did not follow the civil law of the Old Testament freely. For example, they seem largely to have worked with the Romans when it came to capital punishment (e.g., Jesus, James). Stephen would seem to be an exception to the preferred pattern.
But it is clear not only murder remained wrong (e.g., Jas. 2:11), but Jesus elevates the command to include the contemplation of murder (Matt. 5:21-26). The "fulfilling" of the Law mentioned in Matthew 5:17 involved applying the law of love to the concrete command of the Old Testament. The commandment says not to murder, but if the standard is love, then we must not even fantasize, contemplate, or plot violence or harm toward others.
Jesus even extends this principle to name-calling. Calling someone provocative names in hatred is like murder except that it stops short of the action (Matt. 5:22). 1 John 3:15 similarly says that those who hate their brothers and sisters are murderers. What does John have in mind? "How does God’s love abide in anyone who has the world’s goods and sees a brother or sister in need and yet refuses help?" (3:17).
It is thus quite clear that the New Testament elevates the command not to murder significantly. It does so by taking the principle into the realm of the heart. We are to love our friends and enemies. Violence toward others, either in our hearts or with our hands, violate the command not to murder.
4. From time to time, someone will take the command not to kill as an absolute, as a prohibition against killing in any circumstance whatsoever. Does this commandment prohibit war, capital punishment, self-defense, even abortion?
We will be discussing these subjects in the next few articles. Sometimes a principle can be expanded beyond what its original sense was, and we will explore whether such expansion might be the case in relation to some of these types of killing. However, upon a little reflection, it seems clear that the original commandment--at least in the minds of the Israelites--did not have these other permutations in mind when they read this commandment.
5. The word ratsach in the commandment usually applies to the intentional murder of another person. However, it is also used extensively in Numbers in relation to someone who accidentally kills someone else (e.g., Num. 35:6). The cities of refuge in Israel were set up for such people. But there was no protection if you intentionally murdered someone. Clearly adult-adult killing is overwhelmingly what is in view.
It is clear that capital punishment and war were not in view. Exodus, Leviticus, and Deuteronomy all require capital punishment for numerous actions (e.g., Exod. 21:15). A different Hebrew word is used in such cases (moot). Similarly, it would be hard in the extreme to harmonize the conquests of Joshua with the sixth commandment if killing in war were part of what was prohibited.
Did the sixth commandment have an action like abortion in view? It is not at all clear that it was considered such at the time in the Old Testament, although it would seem a legitimate extension of the principle, as we will discuss in a subsequent article. However, in Exodus 21:22, the death of an unborn child as a result of violence toward the mother is not yet treated as murder. It is not likely a situation that any Israelite yet included within the scope of the sixth commandment at that time.
Next Sunday: ET8: Violence in self-defense is regrettable but not wrong.
 Those from other groups often are not considered innocent, and of course killing someone within your group has often been acceptable if s/he were considered "guilty" in some way.