Diamond Sūtra 31

‘And why? Because, O Subhati, if a man were to say that belief in self, belief in a being, belief in life, belief in personality had been preached by the Tathâgata, would he be speaking truly’ Subhuti said: ‘Not indeed, Bhagavat, not indeed, Sugata; he would not be speaking truly. And why? Because, O Bhagavat, what was preached by the Tathagata as a belief in self, that was preached by the Tathigata as no-belief; therefore it is called belief in self.’

Bhagavat said: ‘Thus then, O Subhuti, are all things to be perceived, to be looked upon, and to be believed by one who has entered on the path of the Bodhisattvas. And in this wise are they to be perceived, to be looked upon, and to be believed, that a man should believe neither in the idea of a thing nor in the idea of a no-thing. And why? Because, by saying: The idea of a thing, the idea of a thing indeed, it has been preached by the Tathagata as no-idea of a thing.’