Question: Why do you say that precepts are unchanging and eternal? Don't they change as society changes?
Response: When we think of rules and laws we usually think of what are worldly laws. It is necessary to amend these laws periodically to suit the people and living conditions of the time.
But precepts are supramundane rules, not worldly rules. If you want to transcend this world, the Six Paths, and the Ten Realms, you have to adhere to precepts.
Precepts are rules that all Buddhas and bodhisattvas adhere to in their cultivation over countless lifetimes. They are rules for transcending the Six Paths and the Ten Realms, not worldly rules for daily life. That is why they are unchangeable, the Five Precepts in particular. Do you think the Five Precepts can be changed? Is no killing wrong? How about no stealing, no sexual misconduct, no lying, and no intoxicants? They are unchangeable. They are major precepts by principle and transcend time and space.
~ Based on Ven. Master Chin Kung's 2003 lecture series on the Amitabha Sutra