1.
The Discourse on Ignorance
113.
At Sāvatthī.
Then a certain monk approached the Blessed One, etc.
Seated to one side, that monk said this to the Blessed One -
"'Ignorance, ignorance', venerable sir, is said.
What indeed, venerable sir, is ignorance, and in what way is one gone to ignorance?"
"Here, monk, an ignorant worldling does not understand matter, does not understand the origin of matter, does not understand the cessation of matter, does not understand the practice leading to the cessation of matter;
does not understand feeling...
perception...
does not understand activities... etc.
does not understand the practice leading to the cessation of consciousness.
This is called, monk, ignorance.
And to this extent one is gone to ignorance."
The first.