​MN 10 Satipatthana Sutta: The Foundations of Mindfulness 

Thus have i heard. 

​On one occasion the Blessed One was living in the Kuru country at a town of the Kurus named Kammasadhamma. There he addressed the bhikkhus thus: "Bhikkhus, this is the direct path for the purification of beings, for the surmounting of sorrow and lamentation, for the disappearance of pain and grief, for the attainment of the true way, for the realization of Nibbana - namely these four foundations of mindfulness. What are the four? Here, bhikkhus, a bhikkhu abides contemplating the body as a body, ardent, fully aware, and mindful, having put away covetousness and grief for the world. He abides contemplating feelings as feelings.... He abides contemplating mind as mind....He abides contemplating mind-objects as mind-objects, ardent, fully aware, and mindful, having put away covetousness and grief for the world.

CONTEMPLATION OF THE BODY

1. Mindfulness of Breathing 

Buddha: "And how bhikkhus, does a bhikkhu abide contemplating the body as a body? Here a bhikkhu having 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, being mindful as he breathes in, being mindful as he breathes out. Breathing in long, he understands he breathes in long likewise breathing out long, he understands.
Breathing in short, he understands: 'I breathe in short and i breath out short'. He trains thus: 'I shall breathe in ad out experiencing the whole body of breath'. He trains thus: 'I shall breathe in  and breath out tranquilizing the bodily formation'. Just as a skilled turner or his apprentice, when making a long turn, understands: 'I make a long turn'; or, when making a short turn, understands: 'I make a short turn'; so too, breathing in long, a bhikkhu understands: 'I breathe in long'..... 

INSIGHT

"In this way he abides contemplating the body as a body internally, or he abides contemplating the body as a body externally, or he abides contemplating the body as a body both internally-and externally. Or else he abides contemplating in the body its arising factors, or he abides contemplating in the body its vanishing factors, or he abides contemplating in the body both its arising and vanishing factors. Or else mindfulness that 'there is a body' is simply established in him to the extent necessary for bare knowledge and mindfulness. And he abides independent, not clinging to anything in the world. That is how a bhikkhu abides contemplating the body as a body. 

2. The Four Postures

Buddha:  Again, bhikkhus, when walking, a bhikkhu understands: 'I am walking'; when standing, he understands: 'I am standing'; when sitting he understands: 'I am sitting'; when lying down, he understands: 'I am lying down'; or he understands accordingly however his body is disposed. 
​3. Full Awareness with clear comprehension

"Again, bhikkhus, a bhikkhu is one who acts in full awareness when going forward and returning; who acts in full awareness when looking ahead and looking away; who acts in full awareness when flexing and extending his limbs; who acts in full awareness when wearing his robes and carrying his outer robe and bowl; who acts in full awareness when eating, drinking, consuming food and tasting; who acts in full awareness when defecating and urinating; who acts in full awareness when walking, standing, sitting, falling asleep, waking up, talking, and keeping silent. 

4. Reflection of Foulness - The Bodily Parts

"Again, bhikkhus, a bhikkhu reviews this same body up from the soles of the feet and down from the top of the hair, bounded by skin, full of many kinds of impurity thus: In this body there are head-hairs, body-hairs, nails, teeth, skin, flesh, sinews, bones, bone-marrow, kidneys, heart, liver, diaphragm, spleen, lungs, large intestines, small intestines, contents of the stomach, feces, bile, phlegm, pus, blood, sweat, fat, tears, grease, spittle, snot, oil of the joints, and urine.' Just as though there were a bag with an opening at both ends full of many sorts of grain and a man with good eyes were to open it and review it thus: 'This is hill rice, this is red rice, these are beans.....'; so too, a bhikkhu reviews this same body...as full of many kinds of impurity thus: Tn this body there are head-hairs...and urine.'
​5. Reflection of material Elements

"Again, bhikkhus, a bhikkhu reviews this same body, however it is placed, however disposed, as consisting of elements thus: 'In this body there are the earth element, the water element, the fire element and the air element.' Just like a skilled butcher or his apprentice had killed a cow and with it cut up into pieces; so too, a bhikkhu reviews this same body...as consisting of elements thus: 'In this body there are the earth element, the water element, the fire element, and the air element.'
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6-14. The Nine Charnel Ground Contemplations

"Again, bhikkhus, as though he were to see a corpse thrown aside in a charnel ground, a few days dead, bloated, livid, and oozing matter, a bhikkhu compares this same body with it thus: 'This body too is of the same nature, it will be like that, it is not exempt from that fate.'
In this way he abides contemplating the body ....And he abides independent, not clinging to anything in the world. That too is how a bhikkhu abides contemplating the body as a body.

"Again, as though he were to see a corpse thrown aside in a charnel ground, being devoured by crows, hawks, vultures, or various kinds of worms, a bhikkhu compares this same body with it thus: "This body too is of the same nature, it will be like that, it is not exempt from that fate.' .That too is how a bhikkhu abides contemplating the body as a body.

"Again, as though he were to see a corpse thrown aside in a charnel ground, a skeleton with flesh and blood, held together with sinews...a flesh-less skeleton smeared with blood, held together with sinews...a skeleton without flesh and blood, held together with sinews...disconnected bones scattered in all directions - a bhikkhu compares this same body with it thus: 'This body too is of the same nature, it will be like that, it is not exempt from that fate.' That too is how a bhikkhu abides contemplating the body as a body.

"Again, as though he were to see a corpse thrown aside in a charnel ground, bones bleached white, ... bones heaped up, ...bones rotted and crumbled to dust, a bhikkhu compares this same body with it thus: 'This body too is of the same nature, it will be like that, it is not exempt from that fate.' 

INSIGHT
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"In this way he abides contemplating the body as a body internally, or he abides contemplating the body as a body externally or both. Or else he abides contemplating in the body its arising factors, or he abides contemplating in the body its vanishing factors, or both. Or else mindfulness that 'there is a body' is simply established in him to the extent necessary for bare knowledge and mindfulness. And he abides independent, not clinging to anything in the world. That too is how a bhikkhu abides contemplating the body as a body. 

CONTEMPLATION OF FEELING

"And how, bhikkhus, does a bhikkhu abide contemplating feelings as feelings? Here, when feeling a pleasant feeling, a bhikkhu understands: 'I feel a pleasant feeling'; when feeling a painful feeling, he understands: 'I feel a painful feeling'; when feeling a neither-painful-nor-pleasant feeling, he understands: 'I feel a neither-painful-nor-pleasant feeling.'

When feeling a worldly pleasant feeling, he understands: 'I feel a worldly pleasant feeling'; when feeling an unworldly pleasant feeling, he understands: 'I feel an unworldly pleasant feeling'; when feeling a worldly painful feeling, he understands: 'I feel a worldly painful feeling'; when feeling an unworldly painful feeling, he understands: 'I feel an unworldly painful feeling'; when feeling a worldly neither-painful-nor-pleasant feeling, he understands: 'I feel a worldly neither-painful-nor-pleasant feeling'; when feeling an unworldly neither-painful-nor-pleasant feeling, he understands: 'I feel an unworldly neither-painful-nor-pleasant feeling.' 

INSIGHT

"In this way he abides contemplating feelings as feelings internally, or he abides contemplating feelings as feelings externally, or he abides contemplating feelings as feelings both internally and externally. Or else he abides contemplating in feelings their arising factors, or he abides contemplating in feelings their vanishing factors, or he abides contemplating in feelings both their arising and vanishing factors. Or else mindfulness that 'there is feeling' is simply established in him to the extent necessary for bare knowledge and mindfulness. And he abides independent, not clinging to anything in the world. That is how a bhikkhu abides contemplating feelings as feelings.
 
CONTEMPLATION OF MIND

"And how, bhikkhus, does a bhikkhu abide contemplating mind as mind? Here a bhikkhu understands mind affected by lust/hate/delusion as mind affected by lust, and mind unaffected by lust/hate/delusion as mind unaffected by lust/hate/delusion. He understands contracted/distracted/exalted/unexalted mind as contracted/distracted/exalted/unexalted mind. He understands surpassed/unsurpassed mind as surpassed/unsurpassed mind. He understands concentrated/unconcentrated mind as concentrated/unconcentrated mind. He understands liberated/un-liberated mind as liberated/un-liberated mind. "
​INSIGHT

"In this way he abides contemplating mind as mind internally, or he abides contemplating mind as mind externally, or both. Or else he abides contemplating in mind its arising factors, or he abides contemplating in mind its vanishing factors, or both. Or else mindfulness that 'there is mind' is simply established in him to the extent necessary for bare knowledge and mindfulness. And he abides independent, not clinging to anything in the world. That is how a bhikkhu abides contemplating mind as mind. 

CONTEMPLATION OF MIND-OBJECTS

1. The Five Hindrances

"And how, bhikkhus, does a bhikkhu abide contemplating mind-objects as mind-objects? Here a bhikkhu abides contemplating mind-objects as mind-objects in terms of the five hindrances. Here, there being sensual desire in him, a bhikkhu understands: 'There is sensual desire in me'; or there being no sensual desire in him, he understands: "There is no sensual desire in me'; and he also understands how there comes to be the arising of un-arisen sensual desire, and how there comes to be the abandoning of arisen sensual desire, and how there comes to be the future non-arising of abandoned sensual desire.' Similarly he understands the other four hindrances: ill-will, sloth and torpor, restlessness and remorse & doubt in him; he understands how these hindrances arise and how these hindrances can be abandoned and how there comes to be the future non-arising of these hindrances. 
INSIGHT

"In this way he abides contemplating mind-objects as mind-objects internally, or he abides contemplating mind-objects as mind-objects externally, or both. Or else he abides contemplating in mind-objects their arising factors, or he abides contemplating in mind-objects their vanishing factors, or both. Or else mindfulness that 'there are mind-objects' is simply established in him to the extent necessary for bare knowledge and mindfulness. And he abides independent, not clinging to anything in the world. That is how a bhikkhu abides contemplating mind-objects as mind-objects in terms of the five hindrances. 

2. The Five Aggregates

"Again, bhikkhus, a bhikkhu abides contemplating mind-objects as mind-objects in terms of the five aggregates affected by clinging. Here a bhikkhu understands: 'Such is material form, such its origin, such its disappearance; such is feeling, preception, formations and consciousness; such its origin, such its disappearance. In this way he abides contemplating mind-objects as mind-objects internally, externally, and both ...And he abides independent, not clinging to anything in the world. That is how a bhikkhu abides contemplating mind-objects as mind-objects in terms of the five aggregates affected by clinging. 

3. The Six Bases

"Again, bhikkhus, a bhikkhu abides contemplating mind-objects as mind-objects in terms of the six internal and external bases. Here a bhikkhu understands the eye, he understands forms, and he understands the fetter that arises dependent on both; and he also understands how there comes to be the arising of the un-arisen fetter, and how there comes to be the abandoning of the arisen fetter, and how there comes to be the future non-arising of the abandoned fetter. "He understands the ear, sounds...He understands the nose, odors...He understands the tongue, flavors...He understands the body, tangibles...He understands the mind, mind-objects, and he understands the fetter that arises dependent on both; and he also understands how there comes to be the arising of the un-arisen fetter, and how there comes to be the abandoning of the arisen fetter, and how there comes to be the future non-arising of the abandoned fetter.
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4. The Seven Enlightenment Factors

"Again, bhikkhus, a bhikkhu abides contemplating mind-objects as mind-objects in terms of the seven enlightenment factors. Here, there being the mindfulness enlightenment factor in him, a bhikkhu understands: 'There is the mindfulness enlightenment factor in me'; or there being no mindfulness enlightenment factor in him, he understands:'There is no mindfulness enlightenment factor in me'; and he also understands how there comes to be the arising of the un-arisen mindfulness enlightenment factor, and how the arisen mindfulness enlightenment factor comes to fulfillment by development. "There being the investigation-of-states enlightenment factor in him...There being the energy enlightenment factor him...There being the rapture enlightenment factor in him...There being the tranquility enlightenment factor in him...There being the concentration enlightenment factor in him.. .There being the equanimity enlightenment factor in him, a bhikkhu understands: 'There is the equanimity enlightenment factor in me'; or there being no equanimity enlightenment factor in him...

5. The Four Noble Truths

"Again, bhikkhus, a bhikkhu abides contemplating mind-objects as mind-objects in terms of the Four Noble Truths. Here a bhikkhu understands as it actually is: 'This is suffering'; he understands as it actually is: 'This is the origin of suffering'; he understands as it actually is: 'This is the cessation of suffering'; he understands as it actually is: 'This is the way leading to the cessation of suffering.' 
CONCLUSION

"Bhikkhus, if anyone should develop these four foundations of mindfulness in such a way for seven years, one of two fruits could be expected for him: either final knowledge here and now, or if there is a trace of clinging left, non-return. Let alone seven years, it could take 6 years or 5 years or... 1 year if anyone should develop these four foundations of mindfulness in such a way one of two fruits could be expected for him: either final knowledge here and now, or if there is a trace of clinging left, non-return.  Let alone one year, it could take 7 months, 6 months... one month.. half a month if anyone should develop these four foundations of mindfulness in such a way one of two fruits could be expected for him: either final knowledge here and now, or if there is a trace of clinging left, non-return. Let alone half a month,if anyone should develop these four foundations of mindfulness in such a way for seven days, one of two fruits could be expected for him: either final knowledge here and now, or if there is a trace of clinging left, non-return. 

"So it was with reference to this that it was said: 'Bhikkhus, this is the direct path for the purification of beings, for the surmounting of sorrow and lamentation, for the disappearance of pain and grief, for the attainment of the true way, for the realization of Nibbana - it is namely, these four foundations of mindfulness.'" 

The bhikkhus were satisfied and delighted in the Blessed One's words. 
In summary, Buddha explained the foundations of mindfulness by discussing the contemplation of body, contemplation of feelings, contemplation of the mind and contemplation of mind-objects in details. Those who practice diligently on these foundations of mindfulness meditation will achieve the fruits of enlightenment one day when practiced correctly; it can take maximum of 7 years to do so if they practice correctly and diligently in accordance to this discourse. 
By WHH

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