First among the moral injunctions, accepted and shared by all schools and lineages of the Buddha Dharma, is the precept to abstain from taking life (Anguttara Agama):
A disciple of the Noble Ones, abandoning the taking of life, abstains from taking life. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression.
This is the first gift, the first great gift —original, long-standing, traditional, ancient, untainted, unadulterated from the beginning— that is not open to suspicion, will never be open to suspicion, and is praised by knowledgeable contemplatives and sages.
Is this injunction to abstain from killing solely inclusive of humans? The Buddha gives this instruction in the Griha Vinaya (Rules for Householders, Dharmika Sutra, Kshudraka Agama):
Let him not destroy, or cause to be destroyed, any life at all, or sanction the acts of those who do so. Let him refrain even from hurting any creature, both those that are strong and those that tremble in the world.
If we fail to understand the universality of this injunction, the Buddha clarifies (Kshudraka Agama):
Whether they be creatures of the land or air, whoever harms here any living being, who has no compassion for all that live, let such a one be known as depraved.
And in the Anguttara Agama:
I am a friend of the footless, I am a friend of all bipeds, I am a friend of those with four feet, I am a friend of the many-footed. …
May all creatures, all breathing things, all beings one and all, without exception, experience good fortune only. May they not fall into any harm.
Should we intend to skirt the First Precept by claiming innocence of the deed if others do the killing for us, He adds (Kshudraka Agama):
One should not kill any living being, nor cause it to be killed, nor should one incite any other to kill. Do never injure any being, whether strong or weak, in this entire universe!
In the Brahmajala Sutra, the Buddha says to His disciples, confirming the primacy of the First Precept:
Abandoning the taking of life, the ascetic Gautama dwells refraining from taking life, without stick or sword, scrupulous, compassionate, trembling for the welfare of all living beings. Thus the worldling should praise the Tathagata.
And in the Dharmapada (Udanavarga):
The one who has left all violence, who never harms any beings at all, whether they are moving or still, who neither kills, nor causes to kill, such a one, harmless, is the Holy One!
Innumerable statements proclaiming the primacy of the First Principle can be found throughout the Theravada and Mahayana canons of Buddhist scripture.
The Mahayana sutras in particular are unequivocal in their censure both of killing animals and consuming their flesh and other products.
A disciple of the Buddha must maintain a mind of kindness and cultivate the practice of liberating beings. He should reflect thus:
“All male beings have been my father and all females have been my mother. There is not a single being that has not given birth to me during my previous lives; hence, all beings of the Six Realms are my parents.
“Therefore, when a person kills and eats any of these beings, he thereby slaughters my parents. Furthermore, he kills a body that was once my own, for all elemental earth and water previously served as part of my body, and all elemental fire and wind have served as my basic substance.
“Therefore, I shall always cultivate the practice of liberating beings and in every life be reborn in the eternally abiding Dharma, and teach others to liberate beings as well.”
Whenever a Bodhisattva sees a person preparing to kill animals, he should devise a skilful method to rescue and protect them, freeing them from their suffering and difficulties.
—Buddha Shakyamuni, Brahmajala Sutra
In the Mahaparinirvana Sutra, the Buddha gives extensive arguments against the consumption of flesh:
Animal flesh eating stimulates the emergence of arrogance, which then stimulates delusional imaginations, which then stimulates greed for profit at the expense of compassion for sentient beings. Given the unwholesomeness of such interlocking motivations, it is wise to refrain from eating animal flesh.
From imagination, greed is developed, and through greed the mind becomes dull, complacent, and insensitive. When there is an attachment to such state, then it is difficult to arouse and sustain the impulse to liberate oneself from the wheel of compulsive death and rebirth. …
There is no animal flesh to be regarded as pure by any exception. It does not matter if the giving of animal flesh for us to eat is premeditated or not, asked for or not, or whether extreme hunger is present or not. Therefore it is wise to not eat animal flesh in any circumstance which naturally arises within our life.
Let yogis not eat any animal flesh. All Buddhas teach all people to not eat animal flesh, and especially wish those under Their guidance to not eat animal flesh. Sentient beings who feed on each other will be reborn as carnivores in the animal realm. …
Animal flesh eating is rejected by Buddhas, Bodhisattvas, and Disciples. If a person eats animal flesh out of shamelessness, he or she will not be able to cultivate a wholesome sense of what is appropriate. …
Let a person not give credence to the many rationalizations given to justify animal flesh eating. What word-jugglers say under the influence of their addictive craving for animal flesh is sophistic, delusional, and argumentative. What they imagine that they witnessed, heard, or suspected that the Blessed One has said, or another Buddha said or did, is grossly distorted.
As greed is a hindrance to liberation, so are the objects of greed a hindrance to liberation. Objects of greed like animal flesh eating and consuming alcohol are hindrances to liberation.
A time may come when deluded people may say, “Animal flesh is appropriate food to eat, has no karmic consequences, and is permitted by the Buddha”.
Some will even say that eating animal flesh can be medicinal. It is more like eating the flesh of your only child. Let a yogi be attuned to what is balanced and nourishing to eat, be adverse to consuming animal flesh and alcohol, and with this clarity go about peacefully procuring his food, trusting that what is wanted and needed to sustain a healthy life will be supplied.
Animal flesh eating is forbidden by Me everywhere and for all time for those who abide in compassion.