I read somewhere (don't remember where) that the Buddha mentioned, that he has taught only a fraction of what he could discern with his eye of wisdom (about existence). Does anyone know which Sutra describes this?
That sutta (or, at least, one of those suttas) is sometimes summarized as "a handful of leaves".
"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, etc.