~~~ Atthana metam bhikkhave anavakaso yam
parupakkamena tathagatam jivita voropeyya
anupakkamena bhikkhave tatthagata parinibba yanti. ~~~
O Bhikkhus! There is no means or opportunity to deprive the life of the Buddha by anyone. The Buddhas attain their parinibbana (death) according to their own wishes.
Background History of The Verse
The Buddha uttered the verse “Atthanametam” when Devadatta failed in his plan to assassinate the Buddha.