At Icchānaṅgala
Icchānaṅgala Sutta  (SN 54:11)

On one occasion the Blessed One was staying in Icchānaṅgala in the Icchānaṅgala forest grove. There he addressed the monks: “Monks, I wish to go into seclusion for three months. I am not to be approached by anyone at all except for the one who brings almsfood.”

“As you say, lord,” the monks responded to him. And no one approached the Blessed One except for the one who brought almsfood.

Then the Blessed One, having emerged from seclusion after the passing of three months, addressed the monks: “Monks, if wanderers of other sects ask you, ‘By means of what dwelling, friends, did Gotama the contemplative mostly dwell during the rains residence?’: You, thus asked, should answer them in this way: ‘It was by means of the concentration of mindfulness of breathing that the Blessed One mostly dwelled.’

“There is the case, monks, where mindful1 I breathe in; mindful I breathe out.

“[1] Breathing in long, I discern, ‘I am breathing in long’; or breathing out long, I discern, ‘I am breathing out long.’ [2] Or breathing in short, I discern, ‘I am breathing in short’; or breathing out short, I discern, ‘I am breathing out short.’ [3] I discern,2 ‘I will breathe in sensitive to the entire body.’ I discern, ‘I will breathe out sensitive to the entire body.’ [4] I discern, ‘I will breathe in calming bodily fabrication [in-&-out breathing].’ I discern, ‘I will breathe out calming bodily fabrication.’

“[5] I discern, ‘I will breathe in sensitive to rapture.’ I discern, ‘I will breathe out sensitive to rapture.’ [6] I discern, ‘I will breathe in sensitive to pleasure.’ I discern, ‘I will breathe out sensitive to pleasure.’ [7] I discern, ‘I will breathe in sensitive to mental fabrication [feeling & perception].’ I discern, ‘I will breathe out sensitive to mental fabrication.’ [8] I discern, ‘I will breathe in calming mental fabrication.’ I discern, ‘I will breathe out calming mental fabrication.’

“[9] I discern, ‘I will breathe in sensitive to the mind.’ I discern, ‘I will breathe out sensitive to the mind.’ [10] I discern, ‘I will breathe in gladdening the mind.’ I discern, ‘I will breathe out gladdening the mind.’ [11] I discern, ‘I will breathe in concentrating the mind.’ I discern, ‘I will breathe out concentrating the mind.’ [12] I discern, ‘I will breathe in releasing the mind.’ I discern, ‘I will breathe out releasing the mind.’

“[13] I discern, ‘I will breathe in focusing on inconstancy.’ I discern, ‘I will breathe out focusing on inconstancy.’ [14] I discern, ‘I will breathe in focusing on dispassion [lit: fading].’ I discern, ‘I will breathe out focusing on dispassion.’ [15] I discern, ‘I will breathe in focusing on cessation.’ I discern, ‘I will breathe out focusing on cessation.’ [16] I discern, ‘I will breathe in focusing on relinquishment.’ I discern, ‘I will breathe out focusing on relinquishment.’

“For whatever one rightly speaking would call, ‘a noble dwelling,’ ‘a brahmā dwelling,’ ‘a Tathāgata dwelling,’ it would be the concentration of mindfulness of breathing that he, speaking rightly, would call, ‘a noble dwelling,’ ‘a brahmā dwelling,’ ‘a Tathāgata dwelling.’

“Those monks who are learners, who have yet to attain their hearts’ aspiration, who stay resolved on the unexcelled security from bondage: When the concentration of mindfulness of breathing is developed & pursued by them, it leads to the ending of the effluents.

“Those monks who are arahants, whose effluents are ended, who have reached fulfillment, done the task, laid down the burden, attained the true goal, totally destroyed the fetter of becoming, and who are released through right gnosis: When the concentration of mindfulness of breathing is developed & pursued by them, it leads to a pleasant abiding here-&-now and to mindfulness & alertness.

“For whatever one rightly speaking would call, ‘a noble dwelling,’ ‘a brahmā dwelling,’ ‘a Tathāgata dwelling,’ it would be the concentration of mindfulness of breathing that he, speaking rightly, would call, ‘a noble dwelling,’ ‘a brahmā dwelling,’ ‘a Tathāgata dwelling.’”

Notes

1. Whereas, in the normal formula for breath meditation, the meditator is described as “always mindful (sato’va),” the Buddha describes himself as mindful. This, apparently, is a reference to the fact that he is already always mindful, so he doesn’t have to emphasize the point.

2. Whereas, in the normal formula for breath meditation, the verb in this step and the remaining ones is “he trains himself (sikkhati),” when the Buddha talks of his own practice, he simply says, “I discern (pajānāmi).” He has no further need to train.

See also: SN 22:122; SN 46:4; SN 47:4; SN 52:9