So Krsna spoke all these words five thousand years ago. Apart from taking account of millions of years, because nature's law is the same, so even in those days, five thousand years ago, you'll find the demonic people as they are now. These words about the demons... There were demons like Ravana and Hiranyakasipu, Kamsa. So many demons there were, historical demons. But their process of life was the same as the modern demons. There is no change. Therefore, sastra means it is for all the time, not that sastra was meant in the past for something else, and now something else. That is not the fact. That is, means, sastra, that it does not change. The time, place and atmosphere, according to that, everything is the same.
Lecture on Bhagavad-Gita 16.11-12, Hawaii, 7 February, 1975