Jīvaka, I say that there are three instances in which meat should not be eaten: when it is seen, heard, or suspected [that the living being has been slaughtered for oneself]. I say that meat should not be eaten in these three instances. I say that there are three instances in which meat may be eaten: when it is not seen, not heard, and not suspected [that the living being has been slaughtered for oneself]. I say that meat may be eaten in these three instances.
Gautama Buddha, The Middle Length Discourses of the Buddha: A Translation of the Majjhima Nikaya
buddhism, jīvakasutra, meat, sutra, vegetarianism