You make things clear to you yourself. Not believing what others tell you. If any of you beginners have not had such self-made knowledge yet, know that you have not reached that stage. Work on. If others can, you can. It will not take very long. The knowledge comes to you as you are meditating. Only when you know for sure that all are impermanent, suffering and not self will you not cling to sense objects, as permanent, happy, beautiful, good. Nor will you cling to them as self, soul, the I. All the graspings are done away with. What then? Well, all the defilements are calmed by Ariyan Path and Nibbāna is realised.
"One who has no grasping does not long after things. One who does not long after things is calmed in himself." M. ii 318
Whenever you meditate, you have no obsession with the object noted. So no grasping arises. There is no grasping to what you see, hear, smell, eat, touch or be aware of. They appear to rise each in its time and then pass away. They manifest themselves as impermanent. There is nothing to cling to. They oppress us with their rise and fall. They are all sufferings. There is nothing to cling to as happy, good, or beautiful. They rise and fall as is their nature, so there is nothing to cling to as self, soul, or I, that lives and lasts. All these are made very plain to you. At that the graspings are done away with. Then you realise Nibbāna through Ariyan Path. We will explain this in the light of Dependent Origination and Aggregates.
"The stopping of grasping is from the stopping of craving; the stopping of becoming is from the stopping of grasping; the stopping of birth is from the stopping of becoming; from the stopping of birth; old age and dying, grief, suffering, sorrow, despair, and lamentation are stopped. Thus comes to be the stopping of this entire mass of ill.
M.i. 337; S. ii. 1-3
One who meditates on the mental and material objects that appear at the six doors and knows their intrinsic nature of impermanence, suffering and not-self does not delight in them or cling to them. As he does not grasp them, he makes no effort to enjoy them. As he refuses to make an effort, there arises no karma called "becoming." As no karma arises, there is no new birth. When there is no new birth, there is no occasion for old age, dying, grief, etc. This is how one realises momentary Nibbāna through insight path whenever on meditates. We will explain the realisation by Ariyan Path later.
In Silavanta Sutta earlier quoted, the venerable Sāriputta explained how, if a monk of moral habit meditates on the five grasping aggregates as impermanent, suffering, and not-self, he can become a Stream-winner. If a Stream-winner meditates, he can become a Once-returner. If a Once-returner, a Never-returner; if a Never-returner, an Arahat. Here, to realise the four Ariyan fruitions of Stream-winning, Once-returning, Never-returning, and Arahatship means to realise Nibbāna through the four Ariyan Paths.