The Principle
The Sixth Commandment - "Thou shalt not kill" (Exodus 20:13) - is athe most ancient and absolute statutory prohibition of homicide in the Western legal tradition. Recorded on Sinai and repeated in Deuteronomy 5:17, this seven-word injunction established the foundational moral boundary of all subsequent criminal law: that human life possesses an inviolable sanctity no private individual may transgress. The commandment is not merely a moral exhortation but a legal provision embedded in the covenant code, surrounded by other statutes and carrying implied sanctions that the surrounding narrative makes explicit (Genesis 9:6: "Whoso sheddeth man's blood, by man shall his blood be shed").
Biblical Foundation
The KJV renders the commandment tersely: "Thou shalt not kill" (Exodus 20:13). The Hebrew verb ratsach appears primarily in contexts of unlawful killing - murder or manslaughter - rather than the broader Hebrew harag (to kill in general), suggesting a legal rather than absolute prohibition from the outset. Genesis 9:6 provides the theological rationale: "Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man." The imago Dei grounds homicide prohibition in human dignity. Numbers 35:16-21 enumerates aggravating factors - use of weapons, premeditation, lying in wait - that transform killing into capital murder. Jesus amplifies the commandment in the Sermon on the Mount: "Ye have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment" (Matthew 5:21-22), internalising the prohibition and anticipating modern law's concern with mens rea.
Historical Transmission
The commandment entered Western law through three principal channels. First, Roman law, transmitted through Justinian's Corpus Juris Civilis, absorbed the biblical tradition via the Christianisation of the empire under Constantine and Theodosius, embedding prohibitions of homicide in civil and criminal codes. Second, medieval canon law - especially as systematised by Gratian's Decretum (c. 1140) - held ecclesiastical courts with jurisdiction over homicide cases and articulated detailed distinctions between murder, manslaughter, excusable killing, and justifiable killing that mapped closely onto biblical categories. Third, English common law received these distinctions through Bracton's De Legibus (c. 1235) and reached its most influential codification in Sir William Blackstone's Commentaries on the Laws of England (1765-1769), which explicitly cited the Sixth Commandment as the source of the common law's categorisation of homicide as the supreme crime. Blackstone wrote that homicide is "the killing of any human creature," a category whose moral absolute derived from the biblical prohibition.
Modern Application
Every modern criminal code retains a prohibition on unlawful killing as the apex of criminal offences. The graduated structure of homicide law - first-degree murder (premeditated), second-degree murder (intentional without premeditation), voluntary manslaughter, involuntary manslaughter - closely mirrors the biblical distinctions between killing "with enmity" (Numbers 35:20) and killing "unawares" (Numbers 35:11). The commandment also undergirds constitutional and human rights protections: Article 6 of the International Covenant on Civil and Political Rights declares that "every human being has the inherent right to life," language that echoes the biblical grounding of the Sixth Commandment in the imago Dei. Capital punishment debates in Western democracies continue to engage the commandment directly, with abolitionists citing Matthew 5:21-22 and retentionists citing Genesis 9:6.
Scholarly Debate
Scholars disagree about the precise scope of ratsach. Walter Kaiser argues it applies only to illegal homicide, leaving war, capital punishment, and self-defence outside its remit - a view that shaped most Western legal traditions. Harold Berman's Law and Revolution demonstrates how the Sixth Commandment's transmission through canon law created the Western legal tradition's distinctive category of the criminal as morally guilty agent rather than merely a ritual polluter, as in earlier Roman thinking. More recent work by Christopher Marshall in Crowned with Glory and Honor examines how the Sermon on the Mount's radicalisation of the commandment has influenced restorative justice advocates who argue that criminal law should address the roots of violence rather than merely punish its outcomes.