Venerable Kaccāna asks the Buddha about the cause of the arising of the view regarding those who are not fully awakened Buddhas that they are in fact fully awakened Buddhas.
Giñjakāvasatha sutta - Brick House
At one time, the Blessed One was dwelling in Ñātika, at the Brick House. There, the Blessed One addressed the bhikkhus: "Bhikkhus."
"Venerable sir," those bhikkhus replied to the Blessed One. The Blessed One said this:
"Bhikkhus, dependent on the element, there arises a perception, there arises a view, there arises a thought."
When this was said, the venerable Kaccāna addressed the Blessed One: "Venerable sir, regarding those who are not fully awakened Buddhas, the view arises, 'These are in fact fully awakened Buddhas.' Dependent on what, venerable sir, does this view arise?"
"Mighty, Kaccāna, is this element, namely the element of ignorance. Dependent on an inferior element, Kaccāna, there arises an inferior perception, an inferior view, an inferior thought, an inferior intention, an inferior wish, an inferior aspiration, an inferior person, and an inferior speech. One explains, teaches, presents, establishes, reveals, analyzes, and clarifies what is inferior. His rebirth, I say, is inferior.
Dependent on a middling element, there arises a middling perception, a middling view, a middling thought, a middling intention, a middling wish, a middling aspiration, a middling person, and a middling speech. One explains, teaches, presents, establishes, reveals, analyzes, and clarifies what is middling. His rebirth, I say, is middling.
Dependent on a superior element, there arises a superior perception, a superior view, a superior thought, a superior intention, a superior wish, a superior aspiration, a superior person, and a superior speech. One explains, teaches, presents, establishes, reveals, analyzes, and clarifies what is superior. His rebirth, I say, is superior."