[867] And what, bhikkhus, is the faculty of mindfulness (satindriyaṃ)? Here, bhikkhus, a noble disciple is mindful (sati), possessed of supreme mindfulness and discretion (satinepakka), one who remembers and recollects what was done long ago and what was said long ago. He dwells contemplating the body in the body (kāyānupassanā), ardent (ātāpī), clearly comprehending (sampajāno), mindful, having removed covetousness and grief regarding the world (abhijjhā-domanassa). In feelings (vedanā) … in the mind (citta) … he dwells contemplating dhammas in dhammas, ardent, clearly comprehending, mindful, having removed covetousness and grief regarding the world. This, bhikkhus, is called the faculty of mindfulness.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.