Why Did the Buddha Establish the Precept Against Killing?

The Buddha established precepts, on one hand, to reveal cause and effect, enabling disciples to follow it and avoid punishment by karmic law, preventing them from falling into the three evil destinies or cycling endlessly through the six destinies of rebirth. The fundamental purpose is to protect disciples from harm and to prevent them from harming sentient beings, ensuring no obstructive conditions arise on the path of practice, preventing interruption in the three evil destinies and rendering their efforts in vain. Another reason the Buddha established precepts was to nurture the compassion in disciples, fostering care for sentient beings and protecting their lives. Compassion is inherently the mind of Buddhas and Bodhisattvas. When sentient beings possess compassion, they draw near to the Buddhas and Bodhisattvas and will ultimately become one among them. Had the Buddha not established precepts, disciples would lack behavioral standards; their minds would find no place to settle, leading to confusion. Neither meditative concentration nor wisdom could arise, liberation could not be attained, and tranquil nirvana could not be realized.