Shakyamuni realized clearly that death was approaching. His last sermon was as follows:: "All composite things are by nature impermanent. Work out your salvation with diligence." The Mahaparinibbana Sutra, a standard Pali canonical account, recalls the deathbed scene. The gods Brahma and Indra recited poems. Gods and men wept. "Too soon has the exalted one died!" they cried. "Too soon has the Happy One passed away! Too soon has the light gone out of the world!"
Towards midnight of the same day, the event known in Buddhist terminology as the Parinirvana, or "Final Nirvana," took place. It was a full-moon night and also his eightieth birthday. The Enlightened One passed through progressively higher planes of meditation until he attained entry into Parinirvana.
The death of a truly great man often marks the beginning rather than the end of an era in terms of the progress of human spirit. The difference lies in whether that man lived essentially for his own glory or devoted his life to the pursuit of eternal principles of truth and to the true happiness of all mankind. The image of the dying Buddha is not supposed to evoke sadness as much as a feeling that all beings have the potential to become enlightened and attain release from the sufferings which characterize samsara. His serene, composed, and restful demeanor (he is actually slightly smiling) is meant to communicate his attainment of the highest state of Indian meditation, that of a deep, quiet and blissful sleep known in Sanskrit as 'turiya.' This is precisely the reason why 'Parinirvana' is thought of as the 'final' or 'highest' nirvana.