[1310] "And how, bhikkhus, is mindfulness of breathing (ānāpānasati) developed, how is it cultivated, that it is of great fruit and great benefit? Here, bhikkhus, a bhikkhu, gone to the forest, or to the root of a tree, or to an empty dwelling, sits down, folding his legs crosswise, setting his body erect, and establishing mindfulness in front of him. Just mindful he breathes in, mindful he breathes out. (To be expanded in full up to: he trains thus: 'Contemplating relinquishment, I shall breathe in'; he trains thus: 'Contemplating relinquishment, I shall breathe out.') It is when mindfulness of breathing is developed in this way, bhikkhus, cultivated in this way, that it is of great fruit and great benefit."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.