On Self Control by Maha Ghosananda
Restraining (samvara) is restraint in the six sense bases.
“On seeing a form with the eye, he does not grasp at its signs and features. Since, if he left the eye faculty unguarded, evil unwholesome states of covetousness and grief might invade him, he practices the way of its restraining, he guards the eye faculty, he undertakes the restraining of the eye faculty. [Likewise with the ear, nose, tongue, body, and mind]. Possessing this noble restrain of the faculties, he experiences within himself a bliss that is unsullied.”
“He becomes one who acts in full awareness….” – MN 27:15
This formula is analyzed at VSM I, 53-59. Briefly, the signs (nimitta) are the most distinctive qualities of the object which, when grasped at unmindfully, can kindle defiled thoughts; the features (anabyanjana) are the details that may subsequently catch the attention when the first perceptual contact has not been followed up by restraining. “States of covetousness and grief” signifies the alternative reactions of desire and aversion, attraction and repulsion, towards objects.
The primary factor for exercising this restraint over the sense faculties is mindfulness. A fuller formula for sense restrain is give in many other suttas and analyzed in detail in the Vissudhimagga.
“What more is to be done? You should train yourselves: We will guard the doors of our sense faculties. On seeing a form with the eye, we will not grasp at its signs and features. Since, if we left the eye faculty unguarded, evil unwholesome states of covetousness and grief might invade us, we will practice the way of restraint, we will guard the eye faculty, we will undertake the restrain of the eye faculty…[likewise, nose, tongue, body, mind]…You may think thus: we are possessed of shame and fear of wrongdoing, our bodily conduct, verbal conduct, mental conduct, and livelihood have been purified, and we guard our doors of our sense faculties. That much is enough. And you my rest content with that much. I inform you, I declare to you: You who seek the monks life, do not fall short of the goal of recluse-ship while more is to be done.”