[1357] When this was said, the Venerable Ānanda said this to the Blessed One: "This is the time, Blessed One; this is the time, Fortunate One, for the Blessed One to speak on concentration (samādhi) by mindfulness of breathing (ānāpānasati). Having heard it from the Blessed One, the bhikkhus will bear it in mind."
"Then listen, Ānanda, and attend closely; I shall speak." "Yes, venerable sir," the Venerable Ānanda replied to the Blessed One. The Blessed One said this: "And how, Ānanda, is concentration by mindfulness of breathing developed, how is it cultivated, so that it is of great fruit and great benefit? Here, Ānanda, a bhikkhu, gone to the forest, or gone to the root of a tree, or gone to an empty dwelling, sits down, having folded his legs crosswise, set his body erect, and established mindfulness before him. Just mindful he breathes in … he trains thus: 'Contemplating relinquishment, I shall breathe in'; he trains thus: 'Contemplating relinquishment, I shall breathe out.' Developed in this way, Ānanda, cultivated in this way, concentration by mindfulness of breathing is of great fruit and great benefit."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.