[317] Bhikkhus, a bhikkhu who possesses three qualities dwells with abundant happiness and joy in this very life, and the groundwork has been laid for him for the destruction of the taints (āsava). Which three? He is one who guards the doors of the sense faculties (indriya), who knows moderation in eating, and who is devoted to wakefulness.
And how, bhikkhus, is a bhikkhu one who guards the doors of the sense faculties? Here, bhikkhus, having seen a form with the eye, a bhikkhu does not grasp at its signs (nimitta) or grasp at its features (anubyañjana). Since, if he dwelt with the eye faculty unrestrained, evil, unwholesome states of covetousness and grief might flow in upon him, he practises for its restraint; he protects the eye faculty, he attains restraint over the eye faculty. Having heard a sound with the ear … Having smelled an odour with the nose … Having tasted a flavour with the tongue … Having touched a tangible with the body … Having cognized a mental phenomenon with the mind, he does not grasp at its signs or grasp at its features. Since, if he dwelt with the mind faculty unrestrained, evil, unwholesome states of covetousness and grief might flow in upon him, he practises for its restraint; he protects the mind faculty, he attains restraint over the mind faculty.
Suppose, bhikkhus, on even ground at a crossroads a chariot harnessed to thoroughbreds were standing, with the goad set in place; and a skilled trainer, a charioteer of horses to be tamed, having mounted it, taking the reins in his left hand and the goad in his right hand, would drive it forward and drive it back wherever he wishes and whenever he wishes. Even so, bhikkhus, a bhikkhu trains in the protection of these six sense faculties, trains in their restraint, trains in their taming, trains in their calming. It is in this way, bhikkhus, that a bhikkhu is one who guards the doors of the sense faculties.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.