Thou Shalt Not Kill — or Murder?

Most people learned this commandment in one of two forms, and the difference matters:

You shall not murder.

Exodus 20:13

That is the wording of most modern Bibles. The King James Version, which shaped how English speakers quote the commandments for four centuries, says “Thou shalt not kill.” Read the KJV way, the command seems to forbid all killing: soldiers, police officers, someone defending their family. Read the modern way, it forbids something narrower. Which is right?

In Hebrew the commandment is two words, lo tirtsach: “not” and a form of the verb ratsach. Everything depends on what that verb means.

The short answer: “You shall not murder” is closer to the Hebrew. Ratsach is the word for taking a human life unlawfully, not for every kind of killing. The same law that gives this commandment also allows killing in self-defense and war, and prescribes the death penalty, so it cannot mean “never kill anything.” Christians still disagree about how far it reaches, especially on war and capital punishment. And Jesus took it deeper than any of those debates, to the anger where murder begins. It is one of the ten words in The Ten Commandments: What Each One Means.

Hebrew has several verbs for killing. Harag is the general one, used for killing in battle and even for killing animals. Ratsach, the verb in the commandment, is narrower. It appears a few dozen times in the Old Testament and is never used for animals or for soldiers in war. It describes killing a human being in a way that leaves someone answerable for the blood: usually deliberate murder, and in the laws about cities of refuge, even accidental killing (Numbers 35:11). The point is that human blood is never cheap.

Israel’s own law shows the commandment cannot mean “never kill.” A few chapters later it says, “One who strikes a man so that he dies shall surely be put to death” (Exodus 21:12), and Israel goes to war throughout the Old Testament. Even the King James translators knew the difference: when Jesus quotes this commandment, the KJV renders it “Thou shalt do no murder” (Matthew 19:18). In 1611, “kill” was simply the everyday word.

The reason human life is protected goes back before Sinai, to the flood:

Whoever sheds man’s blood, his blood will be shed by man, for God made man in his own image.

Genesis 9:6

Murder is wrong because every person carries the image of God. To destroy a human life is to strike at something that belongs to him.

If the commandment forbids unlawful killing, the hard questions are about which killing is lawful. The law itself draws one line:

If the thief is found breaking in, and is struck so that he dies, there shall be no guilt of bloodshed for him. If the sun has risen on him, he is guilty of bloodshed.

Exodus 22:2–3

At night, a householder cannot know whether a burglar means to kill, so defending the home is not murder. In daylight, when there are other options, killing the thief is. The principle has lasted: necessary defense is not murder, but killing when you did not have to can be.

Christian traditions build on that in different ways:

• Self-defense. Catholic teaching calls legitimate defense a right, and sometimes a duty for those responsible for others (Catechism §2263–2265). Most Protestant churches agree. The Orthodox tradition is more cautious: even justified killing is treated as a tragedy that calls for repentance.
• War. Most churches follow a “just war” tradition going back to Augustine, which allows war only for a just cause, as a last resort and with limits. Saint Basil still advised soldiers who had killed in battle to stay away from communion for three years. The historic peace churches, such as Mennonites and Quakers, refuse to take part in war at all.
• The death penalty. The Old Testament prescribes it. In 2018 the Catholic Church revised its Catechism to call it “inadmissible” (§2267). Protestants are divided.

Most churches also apply this commandment to life at its beginning and its end. Those questions deserve more than a paragraph, and the traditions’ answers deserve to be heard in full.

Whatever Christians conclude about war and courts, Jesus moved the commandment to a place none of us can stay out of:

You have heard that it was said to the ancient ones, ‘You shall not murder;’ and ‘Whoever murders will be in danger of the judgment.’ But I tell you that everyone who is angry with his brother without a cause will be in danger of the judgment.

Matthew 5:21–22

He goes on: whoever calls his brother “Raca,” an insult something like “empty head,” or “You fool!” is in danger too. The commandment reaches past the act to the contempt that makes the act possible. Very few people commit murder. Almost everyone has written someone off.

The Bible’s first murder shows how it works. Before Cain killed Abel, God warned him: “Sin crouches at the door. Its desire is for you, but you are to rule over it” (Genesis 4:7). Cain did not rule it, and anger became violence in a single chapter. King David’s story moves the same way, from desire to deceit to an arranged death (2 Samuel 11; there is more on that in What Does ‘You Shall Not Covet’ Mean?).

John put it most bluntly: “Whoever hates his brother is a murderer” (1 John 3:15). That is not a claim that hatred and murder do equal damage. It is a diagnosis: they come from the same root, and the commandment wants the root.

Jesus did not stop at forbidding anger. He told his listeners to go and make peace, even if it meant interrupting worship:

If therefore you are offering your gift at the altar, and remember there that your brother has anything against you, leave your gift there before the altar, and go your way. First be reconciled to your brother, and then come and offer your gift.

Matthew 5:23–24

Christian teaching has always read the commandment positively as well. Martin Luther explained it this way in his Small Catechism: we should not hurt or harm our neighbor’s body, “but help and support him in every bodily need.” Not murdering is the floor. Protecting life is the goal.

A few ways that looks in practice:

• Deal with anger early. Anger at injustice can be right; nursed anger turns into contempt. Name it before it hardens.
• Refuse contempt in speech. “Idiot,” “waste of space” and their online equivalents are the modern “Raca.”
• Go first in making peace. Jesus puts the responsibility on the one who remembers the grievance, not the one who caused it.
• Protect the vulnerable. The Good Samaritan kept this commandment by stopping on the road (Luke 10:30–37).

Is it “Thou shalt not kill” or “You shall not murder”?

Both translate the same Hebrew words, lo tirtsach. “You shall not murder” is more precise, because the verb ratsach means unlawful killing of a human being, not killing of any kind. The King James Version says “kill” in Exodus 20:13 but “do no murder” when Jesus quotes it in Matthew 19:18.

Is killing in self-defense a sin?

Most Christian traditions say necessary self-defense is not murder, and Exodus 22:2–3 treats killing a burglar at night as blameless. Catholic teaching calls legitimate defense a right and sometimes a duty. Orthodox Christians often treat any killing, even justified, as calling for repentance, and peace churches refuse violence altogether.

Does killing in war break the commandment?

The Old Testament does not use ratsach for killing in battle, and most churches hold a “just war” view that allows war under strict conditions. Pacifist churches, such as Mennonites and Quakers, believe Jesus’ teaching rules out taking part in war.

Does the commandment forbid the death penalty?

Not in its original setting: the same law prescribes death for murder (Exodus 21:12). Christians disagree about today. The Catholic Church has called the death penalty “inadmissible” since 2018, and Protestant churches hold a range of views.

Which commandment is “Thou shalt not kill”?

It is the sixth commandment in Protestant, Orthodox and Jewish counts, and the fifth in Catholic and Lutheran ones. The words are the same in every Bible (Exodus 20:13; Deuteronomy 5:17); Catholic vs Protestant Ten Commandments explains why the numbers differ.