Maybe this one?
SN 56.31
“In the same way, monks, those things that I have known with direct knowledge but have not taught are far more numerous [than what I have taught]. And why haven’t I taught them? Because they are not connected with the goal, do not relate to the rudiments of the holy life, and do not lead to disenchantment, to dispassion, to cessation, to calm, to direct knowledge, to self-awakening, to Unbinding. That is why I have not taught them.”
Or this one?
MN 63
"And why are they undeclared by me? Because they are not connected with the goal, are not fundamental to the holy life. They do not lead to disenchantment, dispassion, cessation, calming, direct knowledge, self-awakening, Unbinding. That’s why they are undeclared by me.
"And what is declared by me? ‘This is stress,’ is declared by me. ‘This is the origination of stress,’ is declared by me. ‘This is the cessation of stress,’ is declared by me. ‘This is the path of practice leading to the cessation of stress,’ is declared by me. And why are they declared by me? Because they are connected with the goal, are fundamental to the holy life. They lead to disenchantment, dispassion, cessation, calming, direct knowledge, self-awakening, Unbinding. That’s why they are declared by me.
“So, Malunkyaputta, remember what is undeclared by me as undeclared, and what is declared by me as declared.”
Or maybe this one?
DN 29
“A teacher has appeared in the world, worthy & rightly self-awakened. And the Dhamma is well-proclaimed, well-expounded, leading out, conducive to calming, expounded by one who is rightly self-awakened. And we have been instructed in the meaning/goal of the True Dhamma, and the complete holy life has been entirely disclosed to us, made plain, with all its steps collected, complete with miracles, well-proclaimed as far as human beings & devas”
[…]
“But how would one, speaking rightly, say, ‘Seeing, one doesn’t see’? One speaking rightly, would say just this: ‘Seeing, one doesn’t see.’ And what is it that, ‘seeing, one doesn’t see’? Such a well-expounded, entirely complete, well-proclaimed holy life, consummate in all its aspects, complete in all its aspects, with nothing lacking and nothing in excess: This is what one sees. One doesn’t see, ‘If this were taken away from here, it would become purer.’ One doesn’t see, ‘If this were added here, it would become more complete.’ This is called, ‘seeing, one doesn’t see.’"