2.
The Second Discourse on Being Alone
900.
At Sāvatthī.
Then, when the Venerable Anuruddha had gone to a private place and was in seclusion, this reflection arose in his mind:
"For whomsoever the four establishments of mindfulness have been missed, missed for them is the noble path rightly leading to the elimination of suffering;
for whomsoever the four establishments of mindfulness have been undertaken, undertaken for them is the noble path rightly leading to the elimination of suffering."
Then the Venerable Mahāmoggallāna, having known with his mind the reflection in the mind of the Venerable Anuruddha - just as a strong man might extend his bent arm or bend his extended arm, even so - appeared before the Venerable Anuruddha.
Then the Venerable Mahāmoggallāna said this to the Venerable Anuruddha - "In what way, friend Anuruddha, are the four establishments of mindfulness undertaken by a monk?"
"Here, friend, a monk dwells internally observing the body in the body, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world. He dwells externally observing the body in the body, etc. He dwells internally and externally observing the body in the body, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world.
"He dwells internally observing feelings in feelings, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world. He dwells externally observing feelings in feelings, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world. He dwells internally and externally observing feelings in feelings, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world.
Internally in mind, etc. externally in mind, etc. He dwells internally and externally observing mind in mind, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world.
Internally in mental phenomena, etc. externally in mental phenomena, etc. He dwells internally and externally observing mental phenomena in mental phenomena, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world. To this extent, friend, a monk's four establishments of mindfulness have been undertaken. The second.