In the story of the Bible, death is seen as a hostile intruder into the original created order. On this the Bible is clear: a world of sin, killing, and death is not the way things were supposed to be. Apart from specific laws in the Old Testament concerning murder and unintentional killing, the primary means by which the people of God are to understand ethics—how to live and act in every situation—is through imitating and applying the heart and character of God to all of life.
For this reason, the Bible cannot speak to every situation of self-defense that results in someone being killed. The Bible does, however, address the hearts of each person and his or her intentions.
Here the Lord grants a provision in the law for someone who kills a person unintentionally, giving him a city to flee to in which he can remain safe from an avenger of the killing
There is a sense in which this situation may speak to killing in self-defense: to kill a thief who has broken into the home at night is beyond the control of the person who lives there. However, daylight brings a different perspective, a different means of dealing with a thief, and a different judgment if the thief dies. The heart of the law here would seem to be that the death of the thief should never be the intent of the homeowner.
Most modern translations and Greek word study tools agree that the word translated here as “kill” in the KJV (phoneuō) should be translated as “murder.” The word is only used in the New Testament to speak about intentional killing or murder.
In the Bible, Exodus and Numbers provide the most comprehensive teaching on killing in self-defense. It could be argued, however, that the Law of Moses is not meant to be a comprehensive law-code but rather the starting point of godly ethics. And while the civil punishment (or absolution) of those laws no longer apply, the heart behind the laws is no less applicable today than when they were given nearly 3,500 years ago.
We must check that our hearts are not inclined toward hate, murder, and wrathful anger.
Jesus reminds his hearers in Matthew that the heart is the source from which the sin of murder arises. It is certainly true that killing is not always associated with murder. A heart that is bent toward hate and murder, however, with the self-justification that killing in self-defense would be perfectly reasonable would be guilty of an intentional killing even if it was not premeditated.
The word translated “murder” in Exodus 20:13 of the ESV (rāṣaḥ) is sometimes translated “kill” in other translations (for example, the KJV). Many modern translations recognize that the word rāṣaḥ speaks not only to killing person, but intentional killing and other cases of negligent homicide. The word used in Numbers 35:16-18 is the same word used in Exodus 20:13, and the meaning is clearly murder:
The fact that a person used a weapon to strike a fellow human being is reason enough to call the act murder. The context also speaks of enmity as well as lying in wait to kill (i.e., premeditation). In all of these descriptions, there seems to be a heart of hatred in the first person that leads to the death of the second.
In these situations of manslaughter, there is the common element of an unintentionally killing. Whether or not the Bible allows for killing, even in self-defense, comes down to the motive and the intentions of the heart. Generally speaking, it seems that the Bible would allow killing in self-defense given that the defender is trying to resist an attacker or prevent harm from coming to oneself.
In the West and in other places around the world, there is a distinction made between various types of killing. In the United States, murder is legally differentiated by degrees of premediation or intentionality: first, second, and (in just a few states) third degree murder. While only first degree murder is considered premeditated, second degree murder is considered a non-premeditated, intentional killing.
The Bible also speaks of premeditated murder, intentional and unintentional killings (Exodus 21:12-13; Numbers 25:9-34). Laying aside the notion of premeditated murder, there is little distinction in the Law of Moses between general intentional killing and intentional killing in the process of self-defense. Both are characterized by the intent to do harm to another human being. Where the distinction lies is whether killing a person was the goal or the intent.
Killing in self-defense should never be the goal, though at times it is unavoidable. In those unintentional and unavoidable situations, killing in self-defense would not be sinful.
While most examples of self-defense in the Bible occur in the context of war, the book of Esther recounts the Jew’s experience in exile in Persia. In the book of Esther, the Jews are given permission to defend themselves from any enemy that would seek to kill them.