To a Brahman
Brāhmaṇa Sutta  (SN 47:25)

I have heard that on one occasion the Blessed One was staying near Sāvatthī in Jeta’s Grove, Anāthapiṇḍika’s monastery. Then a certain brahman went to the Blessed One and, on arrival, exchanged courteous greetings with him. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there, he said to the Blessed One, “What is the cause, Master Gotama, what is the reason why, when the Tathāgata has totally unbound, the True Dhamma does not last long? And what is the cause, what is the reason why, when the Tathāgata has totally unbound, the True Dhamma does last long?”

“Brahman, it’s from the non-development & non-pursuit of the four establishings of mindfulness that, when the Tathāgata has totally unbound, the True Dhamma does not last long. And it’s from the development & pursuit of the four establishings of mindfulness that, when the Tathāgata has totally unbound, the True Dhamma does last long.

“Which four? There is the case, brahman, where a monk remains focused on the body in & of itself—ardent, alert, & mindful—subduing greed & distress with reference to the world. He remains focused on feelings in & of themselves… the mind in & of itself… mental qualities in & of themselves—ardent, alert, & mindful—subduing greed & distress with reference to the world.

“It’s from the non-development & non-pursuit of these four establishings of mindfulness, brahman, that, when the Tathāgata has totally unbound, the True Dhamma does not last long. And it’s from the development & pursuit of these four establishings of mindfulness that, when the Tathāgata has totally unbound, the True Dhamma does last long.”

When this was said, the brahman said to the Blessed One, “Magnificent, Master Gotama! Magnificent! Just as if he were to place upright what was overturned, to reveal what was hidden, to show the way to one who was lost, or to carry a lamp into the dark so that those with eyes could see forms, in the same way has Master Gotama—through many lines of reasoning—made the Dhamma clear. I go to Master Gotama for refuge, to the Dhamma, & to the Saṅgha of monks. May Master Gotama remember me as a lay follower who has gone for refuge from this day forward, for life.”

See also: SN 16:13; SN 20:7; AN 1:140; AN 1:141; AN 5:79; AN 7:21; AN 7:56