The Ariyan Sangha is the Community of noble persons, all those who have reached the supramundane paths and fruits. This Sangha consists of eight types of individuals joined together into four pairs. The four pairs are:-
The person on the path of stream entry and the stream enterer
The person on the path of once returner and the once returner.
The person on the path of non-returner and the non-returner.
The person on the path of arahantship and the arahant.
What unites all these persons and makes them a community is that they all share a penetration through direct experience of the innermost essence of the Dhamma. All these persons have followed the Buddha’s path to the height of wisdom and seen for themselves the ultimate truth, the truth of the unconditioned. The experience that makes a person an ariyan disciple is called the arising of the eye of the Dhamma. We all have physical eyes by which we can see. We also have mental eyes through which we can understand ideas intellectually, but what the Ariyan person has that an ordinary person lacks is the dhammachakkhu, the eye of truth, the penetrating vision that sees into the real nature of things, the vision that sees the unconditioned element, Nibbana.
Once a person becomes an ariyan disciple he gains absolute confidence in the Triple Gem, in the Buddha, the Dhamma, and the Sangha. He can never go for refuge to any other teacher other than the Buddha, or take as his guiding principle any teaching other than the Dhamma. He has been spiritually reborn, born with a noble birth.
The status of an Ariyan is not established by any formal act of ordination. Any person - monk or nun, layman or laywoman - who penetrates the Dhamma, who arouses the eye of the Dhamma, immediately becomes an Ariyan disciple of the Buddha. Lay persons living at home can also reach all four levels of liberation. But the lay people who have become Arhants are very few and when they do so, according to natural law they immediately renounce the household life and enter the monastic order.
Those who become ariyans have entered the definite path to final liberation. They have stepped beyond the ranks of the multitude caught up in craving and ignorance revolving in birth and death. They can never fall back to the level of a worldling because they have realized the truth by direct experience. They are now bound to reach full enlightenment and final liberation.
The highest of the noble disciples is the arhant. He is the one who never comes back to any form of existence high or low. He has reached enlightenment right in his body, he has cut off all craving and extinguished all defilements. He lives out his day in the bliss of liberation until the break up of the body. With the break up of the body, he attains the final goal, the Nibbana element without residue.
When Buddhists recite "Sangham saranam gachchâmi" (I go for refuge to the Sangha), they are referring to the Ariyan Sangha. The Ariyan Sangha is absolutely essential to the Buddha’s dispensation, for the ariyan disciples stand as living proof of the truth of the Buddha’s teaching. The Ariyans are the ones who have put the teaching to the test, who have practised the path and verified the Dhamma in their own experience. They are the ones who have accomplished the aim of the Dhamma. The Buddha’s teaching aims at transforming ordinary people from worldlings into noble people, at bringing them to the stages of liberation. They are the guides and models. They encourage us to follow the path, since they began as ordinary people like ourselves, but by practising the path they have risen up above the ordinary plane and reached the state of spiritual nobility. Through their own attainments they can give effective instructions to others instruction that is not based on mere guesswork or book learning but on personal experience.