Saṁyutta Nikāya 54.3 1.

Suddhikasutta

Ekadhammavagga Suddhikasutta “Ānāpānassati, bhikkhave, bhāvitā bahulīkatā mahapphalā hoti mahānisaṁsā.

Mindfulness of breathing when developed and cultivated, is of great fruit and great benefit.

Kathaṁ bhāvitā ca, bhikkhave, ānāpānassati kathaṁ bahulīkatā mahapphalā hoti mahānisaṁsā?

And how is mindfulness of breathing developed and cultivated so that it is of great fruit and great benefit?

Idha, bhikkhave, bhikkhu araññagato vā rukkhamūlagato vā suññāgāragato vā nisīdati pallaṅkaṁ ābhujitvā ujuṁ kāyaṁ paṇidhāya parimukhaṁ satiṁ upaṭṭhapetvā.

Here a disciple goes to the forest, to the root of a tree, or to an empty hut, sits down, crosses his legs, holds his body erect, and establishes mindfulness on itself.

So satova assasati, satova passasati …pe…

Ever mindful, he breathes in; ever mindful, he breathes out...

‘paṭinissaggānupassī assasissāmī’ti sikkhati, ‘paṭinissaggānupassī passasissāmī’ti sikkhati.

He trains thus: I shall breathe in contemplating relinquishment; he trains thus: I shall breathe out contemplating relinquishment.

Evaṁ bhāvitā kho, bhikkhave, ānāpānassati evaṁ bahulīkatā mahapphalā hoti mahānisaṁsā”ti. Tatiyaṁ.

It is in this way that mindfulness of breathing, when developed and cultivated, is of great fruit and great benefit.