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
fulfilment in him.

Yasmiṃ samaye, bhikkhave, bhikkhu kāye
kāyānupassī viharati ātāpī sampajāno satimā
vineyya loke abhijjhādomanassaṃ, upaṭṭhitāssa
tasmiṃ samaye sati hoti asammuṭṭhā. Yasmiṃ
samaye, bhikkhave, bhikkhuno upaṭṭhitā sati hoti
asammuṭṭhā, satisambojjhaṅgo tasmiṃ samaye
bhikkhuno āraddho hoti. Satisambojjhaṅgaṃ tasmiṃ
samaye bhikkhu bhāveti, satisambojjhaṅgo tasmiṃ
samaye bhikkhuno bhāvanāpāripūriṃ gacchati.
MN 118

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“And what is a bhikkhu’s resort, his own ancestral
domain? It is the four establishments of
mindfulness. What four? Here, bhikkhus, a bhikkhu
dwells contemplating the body in the body, ardent,
clearly comprehending, mindful, having removed
covetousness and displeasure in regard to the
world. He dwells contemplating feeling in feelings
...

Ko ca, bhikkhave, bhikkhuno gocaro sako pettiko
(Sanskrit: paitṛka / pitṛ ) visayo? Yadidaṃ—cattāro
satipaṭṭhānā. Katame cattāro? Idha, bhikkhave,
bhikkhu kāye kāyānupassī viharati ātāpī sampajāno
satimā, vineyya loke abhijjhādomanassaṃ;
vedanāsu … pe …
SN 47.6

_________

While he dwells contemplating
the body in the body, his mind becomes
concentrated, his corruptions are abandoned, he
picks up that sign. He dwells contemplating feeling
in feelings …

Tassa kāye kāyānupassino
viharato cittaṃ samādhiyati, upakkilesā pahīyanti.
So taṃ nimittaṃ uggaṇhāti. Vedanāsu
vedanānupassī viharati …

SN 47.8

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And how, Ānanda, is there development without
direction? Not directing his mind outwardly, a
bhikkhu understands: ‘My mind is not directed
outwardly.’ Then he understands: ‘It is unconstricted
after and before, liberated, undirected.’ Then he
further understands: ‘I dwell contemplating the body
in the body, ardent, clearly comprehending, mindful;
I am happy.’
“Not directing

Kathañcānanda, appaṇidhāya bhāvanā hoti?
Bahiddhā, ānanda, bhikkhu cittaṃ appaṇidhāya
‘appaṇihitaṃ me bahiddhā cittan’ti pajānāti. Atha
pacchāpure ‘asaṅkhittaṃ vimuttaṃ appaṇihitan’ti
pajānāti. Atha ca pana ‘kāye kāyānupassī viharāmi
ātāpī sampajāno satimā sukhamasmī’ti pajānāti.

SN 47.10

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And how, Ānanda, does a bhikkhu dwell with himself
as his own island, with himself as his own refuge,
with no other refuge; with the Dhamma as his
island, with the Dhamma as his refuge, with no
other refuge?
Here, Ānanda, a bhikkhu dwells contemplating the
body in the body, ardent, clearly comprehending,
mindful, having removed covetousness and
displeasure in regard to the world. He dwells
contemplating feeling in feelings …

Kathañcānanda, bhikkhu attadīpo viharati
attasaraṇo anaññasaraṇo, dhammadīpo
dhammasaraṇo anaññasaraṇo?
Idhānanda, bhikkhu kāye kāyānupassī viharati ātāpī
sampajāno satimā, vineyya loke
abhijjhādomanassaṃ; vedanāsu … pe …
SN 47.13

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“It is, friend, because I have developed and
cultivated the four establishments of mindfulness
that I have attained to greatness of direct
knowledge.
What four?
Here, friend, I dwell contemplating the body in the
body … feeling in feelings …

Catunnaṃ, āvuso, satipaṭṭhānānaṃ bhāvitattā
bahulīkatattā mahābhiññataṃ patto.
Katamesaṃ catunnaṃ?
Idhāhaṃ, āvuso, kāye kāyānupassī viharāmi ātāpī
sampajāno satimā, vineyya loke
abhijjhādomanassaṃ; vedanāsu … pe …
47.28

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“Venerable sir, it would be good if the Blessed One
would teach me the Dhamma in brief, so that,
having heard the Dhamma from the Blessed One, I
might dwell alone, withdrawn, diligent, ardent, and
resolute.”
“In that case, bhikkhu, purify the very beginning of
wholesome states. And what is the beginning of
wholesome states? Here, bhikkhu, dwell restrained
by the restraint of the Patimokkha, accomplished in
good conduct and proper resort, seeing danger in
the slightest faults. Having undertaken the training
rules, train in them. When, bhikkhu, you dwell
restrained by the restraint of the Patimokkha …
seeing danger in the slightest faults, then, based
upon virtue, established upon virtue, you should
develop the four establishments of mindfulness.
“What four? Here, bhikkhu, a bhikkhu dwells
contemplating the body in the body … feeling in
feelings …

Sādhu me, bhante, bhagavā saṃkhittena
dhammaṃ desetu, yamahaṃ bhagavato dhammaṃ
sutvā eko vūpakaṭṭho appamatto ātāpī pahitatto
vihareyyan”ti. “Tasmātiha tvaṃ, bhikkhu, ādimeva
visodhehi kusalesu dhammesu. Ko cādi kusalānaṃ
dhammānaṃ?
Idha tvaṃ, bhikkhu, pātimokkhasaṃvarasaṃvuto
viharāhi ācāragocarasampanno aṇumattesu vajjesu
bhayadassāvī, samādāya sikkhassu sikkhāpadesu.
Yato kho tvaṃ, bhikkhu,
pātimokkhasaṃvarasaṃvuto viharissasi
ācāragocarasampanno aṇumattesu vajjesu
bhayadassāvī samādāya sikkhassu sikkhāpadesu;
tato tvaṃ, bhikkhu, sīlaṃ nissāya sīle patiṭṭhāya
cattāro satipaṭṭhāne bhāveyyāsi.
Katame cattāro? Idha tvaṃ, bhikkhu, kāye
kāyānupassī viharāhi ātāpī sampajāno satimā,
vineyya loke abhijjhādomanassaṃ; vedanāsu … pe

SN 47.46

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"It is, friends, because I dwell with a mind well
established in the four establishments of
mindfulness that the arisen bodily feelings (of sickness) do not persist obsessing my mind.
SN 52.10