It’s all is about the idea, the ideology, the way to design the world.
After teaching dhamma to Subhadda (his last disciple) the Buddha spoke again to Venerable Ananda. “It may be, Ananda, that some of you will say, ‘without the Buddha, the Sublime Teacher, there is no teacher for us’. No, Ananda, you should not think in this way. Whatever doctrine and discipline taught and made known by me will be your teacher when I am gone.”
Then the Buddha addressed all the monks once more, and these were the very last words he spoke:
‘Handa dani bhikkhave amantayami vo vaya dhamma sankhara appamadena Sampadetha”
“Behold, O monks, this is my last advice to you. All component things in the world are changeable. They are not lasting. Work hard to gain your own salvation.”