The Buddha once said this to the Bhikkhus:
"Bhikkhus, as to the source through which perceptions and notions tinged by mental proliferation beset a man: if nothing is found there to delight in, welcome and hold to,
‘It is the single (nature of ) mind
which encompasses all of Samsara and Nirvana. Even though its inherent nature
has existed from the very beginning, you have not recognized it.
(Self-Liberation Through Seeing With Naked Awareness)