Ekaṁ samayaṁ bhagavā vesāliyaṁ viharati ambapālivane. Tatra kho bhagavā bhikkhū āmantesi: “bhikkhavo”ti.
Thus have I heard—At one time, the Blessed One was dwelling at Vesāli, in Ambapālī's Grove. There the Blessed One addressed the bhikkhus: “Bhikkhus.”
“Bhadante”ti te bhikkhū bhagavato paccassosuṁ. Bhagavā etadavoca:
“Venerable sir,” the bhikkhus replied to the Blessed One. The Blessed One said this:
“Sato, bhikkhave, bhikkhu vihareyya sampajāno. Ayaṁ vo amhākaṁ anusāsanī.
“A bhikkhu should dwell with mindfulness and with clear awareness.[1] This is our instruction to you.
Kathañca, bhikkhave, bhikkhu sato hoti? Idha, bhikkhave, bhikkhu kāye kāyānupassī viharati ātāpī sampajāno satimā, vineyya loke abhijjhādomanassaṁ;
And how is a bhikkhu mindful? Here, a bhikkhu dwells observing the body in and of itself, with continuous effort, clearly aware and with excellent recollection, having removed craving and distress with regard to the world;
vedanāsu vedanānupassī viharati ātāpī sampajāno satimā, vineyya loke abhijjhādomanassaṁ;
he dwells observing the felt experience in and of itself, with continuous effort, clearly aware and with excellent recollection, having removed craving and distress with regard to the world;
citte cittānupassī viharati ātāpī sampajāno satimā, vineyya loke abhijjhādomanassaṁ;
he dwells observing the mind in and of itself, with continuous effort, clearly aware and with excellent recollection, having removed craving and distress with regard to the world;
dhammesu dhammānupassī viharati ātāpī sampajāno satimā, vineyya loke abhijjhādomanassaṁ.
he dwells observing the mental qualities in and of themselves, with continuous effort, clearly aware and with excellent recollection, having removed craving and distress with regard to the world.
Evaṁ kho, bhikkhave, bhikkhu sato hoti.
This is how, bhikkhus, a bhikkhu is mindful.
Kathañca, bhikkhave, bhikkhu sampajāno hoti? Idha, bhikkhave, bhikkhu abhikkante paṭikkante sampajānakārī hoti, ālokite vilokite sampajānakārī hoti, samiñjite pasārite sampajānakārī hoti, saṅghāṭipattacīvaradhāraṇe sampajānakārī hoti, asite pīte khāyite sāyite sampajānakārī hoti, uccārapassāvakamme sampajānakārī hoti, gate ṭhite nisinne sutte jāgarite bhāsite tuṇhībhāve sampajānakārī hoti. Evaṁ kho, bhikkhave, bhikkhu sampajānakārī hoti.
And how is a bhikkhu clearly aware? Here, a bhikkhu is one who acts with clear awareness when going forward and returning; who acts with clear awareness when looking ahead and looking away; who acts with clear awareness when flexing and extending his limbs; who acts with clear awareness in wearing his robes and carrying his outer robe and bowl; who acts with clear awareness when eating, drinking, consuming food, and tasting; who acts with clear awareness when defecating and urinating; who acts with clear awareness when walking, standing, sitting, falling asleep, waking up, talking, and keeping silent. This is how, bhikkhus, a bhikkhu is clearly aware.
Sato, bhikkhave, bhikkhu vihareyya sampajāno. Ayaṁ vo amhākaṁ anusāsanī”ti.
A bhikkhu should thus dwell with mindfulness and with clear awareness. This is our instruction to you.”
A dwelling of mindfulness and clear awareness, when cultivated and frequently practiced, leads to radical comprehension. Read in AN 4.41 Samādhibhāvanā sutta - Developments of Collectedness.