These two suttas build upon the concept of the luminous mind (pabhassara citta), explaining why mind-development (cittabhāvanā) is impossible for the uninstructed person, but possible for the instructed noble disciple.
AN 1.51: The Uninstructed Worldling
Pali
“पभस्सरमिदं, भिक्खवे, चित्तं। तञ्च खो आगन्तुकेहि उपक्किलेसेहि उपक्किलिट्ठं। तं अस्सुतवा पुथुज्जनो यथाभूतं नप्पजानाति। तस्मा ‘अस्सुतवतो पुथुज्जनस्स चित्तभावना नत्थी’ति वदामी”ति।”
Sanskrit Chaya
“प्रभास्वरमिदं भिक्षवश्चित्तम्। तच्च खल्वागन्तुकैरुपक्लेशैरुपक्लिष्टम्। तदश्रुतवान् पृथग्जनो यथाभूतं न प्रजानाति। तस्माद् ‘अश्रुतवतः पृथग्जनस्य चित्तभावना नास्ती’ति वदामीति।”
“This mind, monks, is luminous. But it is defiled by adventitious defilements. The uninstructed worldling does not understand this as it really is. Therefore, I say that for the uninstructed worldling there is no development of the mind.”
AN 1.52: The Instructed Noble Disciple
Pali
“पभस्सरमिदं, भिक्खवे, चित्तं। तञ्च खो आगन्तुकेहि उपक्किलेसेहि विप्पमुत्तं। तं सुतवा अरियसावको यथाभूतं पजानाति। तस्मा ‘सुतवतो अरियसावकस्स चित्तभावना अत्थी’ति वदामी”ति।”
Sanskrit Chaya
“प्रभास्वरमिदं भिक्षवश्चित्तम्। तच्च खल्वागन्तुकैरुपक्लेशैर्विप्रमुक्तम्। तच्छ्रुतवान् आर्यश्रावको यथाभूतं प्रजानाति। तस्माच् ‘छ्रुतवत आर्यश्रावकस्य चित्तभावनास्ती’ति वदामीति।”
“This mind, monks, is luminous. And it is freed from adventitious defilements. The instructed noble disciple understands this as it really is. Therefore, I say that for the instructed noble disciple there is development of the mind.”

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