Paṭhamaphalasutta
“Ānāpānassati, bhikkhave, bhāvitā bahulīkatā mahapphalā hoti mahānisaṁsā. Kathaṁ bhāvitā ca, bhikkhave, ānāpānassati kathaṁ bahulīkatā mahapphalā hoti mahānisaṁsā? Idha, bhikkhave, bhikkhu araññagato vā rukkhamūlagato vā suññāgāragato vā nisīdati pallaṅkaṁ ābhujitvā ujuṁ kāyaṁ paṇidhāya parimukhaṁ satiṁ upaṭṭhapetvā. So satova assasati, satova passasati …pe… ‘paṭinissaggānupassī assasissāmī’ti sikkhati, ‘paṭinissaggānupassī passasissāmī’ti sikkhati. Evaṁ bhāvitā kho, bhikkhave, ānāpānassati evaṁ bahulīkatā mahapphalā hoti mahānisaṁsā. Evaṁ bhāvitāya kho, bhikkhave, ānāpānassatiyā evaṁ bahulīkatāya dvinnaṁ phalānaṁ aññataraṁ phalaṁ pāṭikaṅkhaṁ— diṭṭheva dhamme aññā, sati vā upādisese anāgāmitā”ti.
Fruits (1st)
“Mendicants, when mindfulness of breathing is developed and cultivated it’s very fruitful and beneficial. And how is mindfulness of breathing developed and cultivated to be very fruitful and beneficial? It’s when a mendicant—gone to a wilderness, or to the root of a tree, or to an empty hut—sits down cross-legged, sets their body straight, and brings mindfulness to the present. Just mindful, they breathe in. Mindful, they breathe out. … They practice like this: ‘I’ll breathe in observing letting go.’ They practice like this: ‘I’ll breathe out observing letting go.’ Mindfulness of breathing, when developed and cultivated in this way, is very fruitful and beneficial. When mindfulness of breathing is developed and cultivated in this way you can expect one of two results: enlightenment in this very life, or if there’s residue left behind, non-return.”