Thou shalt not kill.
~ Ex 20:13, Dt 5:17
The taking of human life is very serious in God’s eyes. When a human arbitrarily takes the life of another human, they are acting as judge, jury and executioner.
Some condemn the death penalty, and they appeal to “Thou shalt not kill” as the basis. However, that viewpoint ignores the very obvious fact that God has empowered the state to make decisions about guilt or innocence and carry out the appropriate punishment.
The word for “kill” is “ratsach”, Strong’s H7523. Modern versions render this as “You shall not murder”, which distinguishes this from other forms of taking a life. For example, it never refers to the taking of animal life. In 47 occurrences, it always refers to the taking of a human life under dubious or accidental circumstances. The “slayer” for example might be able to seek protection in a city of refuge (Jos 21:21, 27). Even though Ahab was king, he still was expected to follow the law. Yet, he “killed” Naboth for his vineyard, an act which greatly displeased God.
In contrast, the word “harag”, Strong’s H2026, more closely matches our English word “kill”. It can refer to animals, the slaying of an innocent person, the taking of one’s life through some type of judgement, or killing someone in warfare.
The OT outlines various types of crimes that were to be punishable by death. It is important to differentiate that these were crimes, and there were rules to follow before the death penalty could be carried out. Elders and judges were appointed to maintain the law (Ex 22:9), and the death penalty could only be carried out if there were at least 2 witnesses (Nu 35:30; Dt 17:6). The witnesses would be the ones to cast the first stone (Dt 17:7; Jn 8:7). Under these circumstances, it was far more likely for a guilty man to live than an innocent man be put to death. To circumvent these laws or to give into corruption was considered as serious as murder (Dt 19:15-21).
Warfare is a larger topic that deserves its own article. What should be remembered is that OT warfare was authorized by God. He decided if or when Israel would engage in warfare. Apparently, this was done through the Urim and Thummim. Without prophets and without the Urim and Thummim, we have to rely upon human judgement as to when to go to war. Naturally, there is an inherent problem with relying upon human judgement in such matters (Pr 16:25).
What is more important, though, is that Jesus said that in this present evil age we are to be as harmless as doves (Mt 10:16) and not engage in this world’s warfare (Jn 18:36).
Human life is precious to God. He does not even desire the death of the wicked (Eze 33:11), but there are attitudes that cannot be allowed to prevail else they affect innocent people as well (Nu 35:33; Eze 13:19; Dt 12:28; 17:7; 19:19; 21:21; 22:21, 24; 24:7).
We are created in the image of God (Ge 1:27), and as a result, we should not even curse people with our words (Jas 3:9). Each of us has the potential to become children of God. To take a life is serious business because to take a life is to take the life of a potential child of God.