The Buddha describes how he knows of the release, liberation and independence for living beings.

Nimokkha sutta - Release

At Sāvatthi.

Then, when the night had advanced, a certain deity having a beautiful appearance, illuminating almost the entire Jeta's grove, approached the Blessed One. Having approached and greeted him, she stood to one side. Standing to one side, the deity said to the Blessed One: "Do you know, sir, the release, liberation, and independence for living beings?"

"I know, friend, the release, liberation, and independence for living beings," replied the Blessed One.

"In what way then, sir, do you know the release, liberation, and independence for living beings?" asked the deity.

"With the exhaustion of delight in existence, with the exhaustion of perception and consciousness; with the ending of feelings and with tranquility, Thus indeed, friend, I know; the release, liberation, and independence for living beings."