​MN 118 Anapanasati Sutta: Mindfulness of Breathing 

​INTRODUCTORY SECTION

Thus have i heard. On one occasion the Blessed One was living at Savatthi in the Eastern Park, in the Palace of Migara's Mother, together with many very well-known elder disciples - the venerable Sariputta, the venerable Maha Moggallana, the venerable Maha Kassapa, the venerable Maha Kaccana, the venerable Maha Kotthita, the venerable Maha Kappina, the venerable Maha Cunda, the venerable Anuruddha, the venerable Revata, the venerable Ananda, and other very well-known elder disciples.

Now on that occasion elder bhikkhus had been teaching and instructing new bhikkhus; some elder bhikkhus had been teaching and instructing ten new bhikkhus, some elder bhikkhus had been teaching and instructing twenty...thirty... forty new bhikkhus. And the new bhikkhus, taught and instructed by the elder bhikkhus, had achieved successive stages of high distinction.

On that occasion - the Uposatha day of the fifteenth, on the full-moon night of the Pavarana ceremony - the Blessed One was seated in the open surrounded by the Sangha of bhikkhus. Then, surveying the silent Sangha of bhikkhus, he addressed them thus: "Bhikkhus, I am content with this progress. My mind is content with this progress. So arouse still more energy to attain the unattained, to achieve the unachieved, to realize the unrealized. I shall wait here at Savatthi for the Komudi full moon of the fourth month."

The bhikkhus of the countryside heard: "The Blessed One will wait there at Savatthi for the Komudi full moon of the  fourth month." And the bhikkhus of the countryside left in due course for Savatthi to see the Blessed One.

And elder bhikkhus still more intensively taught and instructed new bhikkhus; some elder bhikkhus taught and instructed ten new bhikkhus, some elder bhikkhus taught and instructed twenty...thirty...forty new bhikkhus. And the new bhikkhus, taught and instructed by the elder bhikkhus, achieved successive stages of high distinction.

On that occasion - the Uposatha day of the fifteenth, the full-moon night of the Komudi full moon of the fourth month the Blessed One was seated in the open surrounded by the Sangha of bhikkhus. Then, surveying the silent Sangha of bhikkhus, he addressed them thus:"Bhikkhus, this assembly is free from prattle, this assembly is free from chatter. It consists purely of heartwood. Such is this Sangha of bhikkhus, such is this assembly. Such an assembly as is worthy of gifts, worthy of hospitality, worthy of offerings, worthy of reverential salutation, an incomparable field of merit for the world - such is this Sangha of bhikkhus, such is this assembly. Such an assembly that a small gift given to it becomes great and a great gift greater - such is this Sangha of bhikkhus, such is this assembly. Such an assembly as is rare for the world to see - such is this Sangha of bhikkhus, such is this assembly. Such an assembly as would be worth journeying many leagues with a travel-bag to see - such is this Sangha of bhikkhus, such is this assembly."

"In this Sangha of bhikkhus there are bhikkhus who are arahants with taints destroyed, who have lived the holy life, done what had to be done, laid down the burden, reached the true goal, destroyed the fetters of being, and are completely liberated through final knowledge - such bhikkhus are there in this Sangha of bhikkhus. In this Sangha of bhikkhus there are bhikkhus who, with the destruction of the five lower fetters, are due to reappear spontaneously in the Pure Abodes and there attain final Nibbana, without ever returning from that world - such bhikkhus are there in this Sangha of bhikkhus."

"In this Sangha of bhikkhus there are bhikkhus who, with the destruction of three fetters and with the attenuation of lust, hate, and delusion, are once-returners, returning once to this world to make an end of suffering - such bhikkhus are there in this Sangha of bhikkhus. In this Sangha of bhikkhus there are bhikkhus who, with the destruction of the three fetters, are stream-enterers, no longer subject to perdition, bound for deliverance, headed for enlightenment - such bhikkhus are there in this Sangha of bhikkhus. "

"In this Sangha of bhikkhus there are bhikkhus who abide devoted to the development of the four foundations of mindfulness - such bhikkhus are there in this Sangha of bhikkhus. In this Sangha of bhikkhus there are bhikkhus who abide devoted to the development of the four right kinds of striving...of the four bases for spiritual power...of the five faculties...of the five powers... of the seven enlightenment factors...of the Noble Eightfold Path - such bhikkhus are there in this Sangha of bhikkhus. "

"In this Sangha of bhikkhus there are bhikkhus who abide devoted to the development of loving-kindness....of compassion...of appreciative joy...of equanimity...of the meditation on foulness...of the perception of impermanence - such bhikkhus are there in this Sangha of bhikkhus. In this Sangha of bhikkhus there are bhikkhus who abide devoted to the development of mindfulness of breathing. "

MINDFULNESS OF BREATHING

"Bhikkhus, when mindfulness of breathing is developed and cultivated, it is of great fruit and great benefit. When mindfulness of breathing is developed and cultivated, it fulfills the four foundations of mindfulness. When the four foundations of mindfulness are developed and cultivated, they fulfill the seven enlightenment factors. When the seven enlightenment factors are developed and cultivated, they fulfill true knowledge and deliverance."

"And how, bhikkhus, is mindfulness of breathing developed and cultivated, so that it is of great fruit and great benefit?  Here a bhikkhu, gone to the forest or to the root of a tree or to an empty hut, sits down; having folded his legs crosswise, set his body erect, and established mindfulness in front of him, ever mindful he breathes in, mindful he breathes out. Breathing in long, he understands:'I breathe" in long'; or breathing out long, he understands: 'I breathe out long.' Breathing in short, he understands: 'I breathe in short'; or breathing out short, he understands: 'I breathe out short.' He trains thus: 'I shall breathe in experiencing the whole body of breath'; he trains thus: 'I shall breathe out experiencing the whole body of breath.' He trains thus: 'I shall breathe in tranquilizing the bodily formation'; he trains thus: 'I shall breathe out tranquilizing the bodily formation.'"

"He trains thus: 'I shall breathe in experiencing rapture'; he trains thus: 'I shall breathe out experiencing rapture.' He trains thus: 'I shall breathe in experiencing pleasure'; he trains thus: 'I shall breathe out experiencing pleasure.' He trains thus: 'I shall breathe in experiencing the mental formation'; he trains thus: 'I shall breathe out experiencing the mental formation.' He train thus: 'I shall breathe in tranquilizing the mental formation'; he trains thus: 'I shall breathe out tranquilizing the mental formation.' "He trains thus: 'I shall breathe in experiencing the mind'; he trains thus: 'I shall breathe out experiencing the mind.' He trains thus: 'I shall breathe in gladdening the mind'; he trains thus: 'I shall breathe out gladdening the mind.' "

"He trains thus: 'I shall breathe in concentrating the mind'; he trains thus: 'I shall breathe out concentrating the mind.' He trains thus: 'I shall breathe in liberating the mind'; he trains thus: 'I shall breathe out liberating the mind.' "He trains thus: 'I shall breathe in contemplating impermanence'; he trains thus: 'I shall breathe out contemplating impermanence.' He trains thus: 'I shall breathe in contemplating fading away'; he trains thus: 'I shall breathe out contemplating fading away.' He trains thus: 'I shall breathe in contemplating cessation'; he trains thus: 'I shall breathe out contemplating cessation.' He trains thus: 'I shall breathe in contemplating relinquishment'; he trains thus: 'I shall breathe out contemplating relinquishment.'" 

"Bhikkhus, that is how mindfulness of breathing is developed and cultivated, so that it is of great fruit and great benefit. "

FULFILLMENT OF THE FOUR FOUNDATIONS OF MINDFULNESS

"And how, bhikkhus, does mindfulness of breathing, developed and cultivated, fulfill the four foundations of mindfulness? "

"Bhikkhus, on whatever occasion a bhikkhu, breathing in long, understands: 'I breathe in long,' or breathing out long, understands: 'I breathe out long'; breathing in short, understands: 'I breathe in short,' or breathing out short, understands: 'I breathe out short'; trains thus: 'I shall breathe in experiencing the whole body of breath'; trains thus: 'I shall breathe out experiencing the whole body of breath'; trains thus: 'I shall breathe in tranquilizing the bodily formation'; trains thus: 'I shall breathe out tranquilizing the bodily formation' - on that occasion a bhikkhu abides contemplating the body as a body, ardent, fully aware, and mindful, having put away covetousness and grief for the world. "

"I say that this is a certain body among the bodies, namely, in-breathing and out-breathing. That is why on that occasion a bhikkhu abides contemplating the body as a body, ardent, fully aware, and mindful, having put away covetousness and grief for the world."

"Bhikkhus, on whatever occasiona bhikkhu trains thus: 'I shall breathe in experiencing rapture'; trains thus: 'I shall breathe out experiencing rapture'; trains thus: 'I shall breathe in experiencing pleasure'; trains thus: 'I shall breathe out experiencing pleasure'; trains thus: 'I shall breathe in experiencing the mental formation'; trains thus: 'I shall breathe out experiencing the mental formation'; trains thus: 'I shall breathe in tranquilizing the mental formation'; trains thus: 'I shall breathe out tranquilizing the mental formation' - on that occasion a bhikkhu abides contemplating feelings as feelings, ardent, fully aware, and mindful, having put away covetousness and grief for the world. I say that this is a certain feeling among the feelings, namely, giving close attention to in-breathing and out-breathing.That is why on that occasion a bhikkhu abides contemplating feelings as feelings, ardent, fully aware, and mindful, having put away covetousness and grief for the world."

"Bhikkhus, on whatever occasion a bhikkhu trains thus: 'I shall breathe in experiencing the mind'; trains thus: 'I shall breathe out experiencing the mind'; trains thus: 'I shall breathe in gladdening the mind'; trains thus: 'I shall breathe out gladdening the mind'; train thus: 'I shall breathe in concentrating the mind'; trains thus: 'I shall breathe out concentrating the mind'; trains thus: 'I shall breathe in liberating the mind'; trains thus: 'I shall breathe out liberating the mind' - on that occasion a bhikkhu abides contemplating mind as mind, ardent, fully aware, and mindful, having put away covetousness and grief for the world. I do not say that there is the development of mindfulness of breathing for one who is forgetful, who is not fully aware. That is why on that occasion a bhikkhu abides contemplating mind as mind, ardent, fully aware, and mindful, having put away covetousness and grief for the world."
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"Bhikkhus, on whatever occasion a bhikkhu trams thus: 'I shall breathe in contemplating impermanence'; trains thus: 'I shall breathe out contemplating impermanence'; trams thus: 'I shall breathe in contemplating fading away'; trains thus: 'I shall breathe out contemplating fading away'; trains thus: 'I shall breathe in contemplating cessation'; trains thus: 'I shall breathe out contemplating cessation'; trams thus: 'I shall breathe in contemplating relinquishment'; trains thus: 'I shall breathe out contemplating relinquishment' - on that occasion a bhikkhu abides contemplating mind-objects as mind-objects, ardent, fully aware, and mindful, having put away covetousness and grief for the world. Having seen with wisdom the abandoning of covetousness and grief, he closely looks on with equanimity. That is why on that occasion a bhikkhu abides contemplating mind-objects as mind-objects, ardent, fully aware, and mindful, having put away covetousness and grief for the world."

"Bhikkhus, that is how mindfulness of breathing, developed and cultivated, fulfils the four foundations of mindfulness. ​"

​FULFILMENT OF THE SEVEN ENLIGHTENMENT FACTORS

​"And how, bhikkhus, do the four foundations of mindfulness, developed and cultivated, fulfill the seven enlightenment factors?  Bhikkhus, on whatever occasion a bhikkhu abides contemplating the body as a body, ardent, fully aware, and mindful, having put away covetousness and grief for the world - on that occasion unremitting mindfulness is established in him. On whatever occasion unremitting mindfulness is established in a bhikkhu - on that occasion the mindfulness enlightenment factor is aroused in him, and he develops it, and by development, it comes to fulfillment in him."

"Abiding thus mindful, he investigates and examines that state with wisdom and embarks upon a full inquiry into it. On whatever occasion, abiding thus mindful, a bhikkhu investigates and examines that state with wisdom and embarks upon a full inquiry into it - on that occasion the investigation-of-states enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him."

"In one who investigates and examines that state with wisdom and embarks upon a full inquiry into it, tireless energy is aroused. On whatever occasion tireless energy is aroused in a bhikkhu who investigates and examines that state with wisdom and embarks upon a full inquiry into it - on that occasion the energy enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him."

"In one who has aroused energy, unworldly rapture arises. On whatever occasion unworldly rapture arises in a bhikkhu who has aroused energy -on that occasion the rapture enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him. In one who is rapturous, the body and the mind become tranquil. On whatever occasion the body and the mind become tranquil in a bhikkhu who is rapturous - on that occasion the tranquility enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him."
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"In one whose body is tranquil and who feels pleasure, the mind becomes concentrated. On whatever occasion the mind becomes concentrated in a bhikkhu whose body is tranquil and who feels pleasure - on that occasion the concentration enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him.  He closely looks on with equanimity at the mind thus concentrated. On whatever occasion a bhikkhu closely looks on with equanimity at the mind thus concentrated - on that occasion the equanimity enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him. "

"Bhikkhus, on whatever occasion a bhikkhu abides contemplating feelings as feelings, ardent, fully aware, and mindful, having put away covetousness and grief for the world...(repeat as at above)...the equanimity enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him. Bhikkhus, on whatever occasion a bhikkhu abides contemplating mind as mind, ardent, fully aware, and mindful, having put away covetousness and grief for the world ...(repeat as at above)...the equanimity enlightenment is aroused in him, and he develops it, and by development it comes to fulfillment in him. "
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"Bhikkhus, on whatever occasion a bhikkhu abides contemplating mind-object as mind-objects, ardent, fully aware, and mindful, having put away covetousness and grief for the world...(repeat as above).....the equanimity enlightenment factor is aroused in him, and he develops it, and by development it comes to fulfillment in him. "

"Bhikkhus, that is how the four foundations of mindfulness, developed and cultivated, fulfill the seven enlightenment factors."

FULFILLMENT OF TRUE KNOWLEDGE AND DELIVERANCE

"And how, bhikkhus, do the seven enlightenment factors, developed and cultivated, fulfill true knowledge and deliverance?  Here, bhikkhus, a bhikkhu develops the mindfulness enlightenment factor, which is supported by seclusion, dispassion, and cessation, and ripens in relinquishment. He develops the investigation-of-states enlightenment factor...the energy enlightenment factor...the rapture enlightenment factor...the tranquility enlightenment factor...the concentration enlightenment factor...the equanimity enlightenment factor, which is supported by seclusion, dispassion, and cessation, and ripens in relinquishment."

"Bhikkhus, that is how the seven enlightenment factors, developed and cultivated, fulfill true knowledge and deliverance."

That is what the Blessed One said. The bhikkhus were satisfied and delighted in the Blessed One's words.

In summary, The Buddha first explains the four stages of enlightenment followed by how the four foundations of mindfulness can lead one to achieve liberation. Then Buddha elaborated on the mindfulness of breathing, the fulfillment of the four foundations of mindfulness (contemplation of body, feelings, mind and mind-objects) and the fulfillment of the seven enlightenment factors and finally reaching the final knowledge and deliverance. 

References: 
1. www.accesstoinsight.org
2. https://suttacentral.net/
3. The middle length discourses of the Buddha (Bhikkhu Bodhi)