Do not kill (First Precept)

Buddhists affirm as the first of the Five Precepts the undertaking to abstain from taking life. Expressed as a training rule the practitioner takes upon themselves rather than a command imposed from without, it enjoins non-harm toward all sentient beings, human and animal, and is rooted in the wider ethic of compassion (karuna) and loving-kindness (metta) and in the recognition that all beings shrink from death. The precept restrains not only killing but the intention behind it, since Buddhist ethics weighs action above all by the state of mind that drives it.

The precept's strictness is calibrated by role: the Vinaya makes killing a human being one of the four parajika offences that expel a monk or nun from the monastic order outright, with no allowance made even for self-defence, while lay Buddhists undertake the precept as a voluntary training rather than a punishable law, leaving room for individual conscience in extreme situations. That gap has generated real historical argument: Buddhist-majority states have waged war and executed criminals throughout history, and during Sri Lanka's civil war (1983 to 2009) some Sinhalese Buddhist monks and lay writers argued that defending the Buddhist nation could be a lesser evil justified by compassion for the greater number, a position other Buddhist teachers rejected as a rationalisation incompatible with the precept's plain sense.

The precept is held throughout the Buddhist world (Theravada, Mahayana, and Vajrayana alike), as the foundation of moral conduct (sila), the first stage of the path. Its emphasis on intention distinguishes the Buddhist formulation from a bare prohibition: harm done knowingly and willingly carries the heaviest karmic weight. The value connects to Buddhist attitudes toward vegetarianism, warfare, and the treatment of animals, and it parallels the non-violence (ahimsa) central to the neighbouring Indian traditions of Hinduism and, most rigorously, Jainism, while Buddhism frames it as a voluntary training in compassion. Whether the precept requires vegetarianism has divided the tradition since its early centuries.

The Pali Canon records the Buddha permitting monks to eat meat under the threefold purity rule, so long as they had not seen, heard, or suspected that the animal was killed specifically for them, and he is said to have declined a proposal by his cousin Devadatta to make vegetarianism obligatory for the order. Several Mahayana texts, notably the Lankavatara Sutra, argue instead that eating any meat implicates the eater in killing and contradicts the compassion the precept requires, a position that shaped the strict vegetarianism common in Chinese and Vietnamese monastic Buddhism, while Theravada and Tibetan monastics have more often continued to eat meat obtained without direct participation in the killing.