佛說觀佛三昧海經 2.31

2.31

“Sitting upon this seat, the Buddha eliminated the three hindrances and completed the path to bodhi. The realm of the Buddha’s mind cannot be exhaustively spoken of; were it to be explained at length, not a single sentient being, up to even the bodhisattvas of the tenth ground, could know or comprehend it. Therefore, within this mark of the white ūrṇā, it is kept concealed and not spoken.