The propagation of Buddhism in Sri Lanka in the third century B.C. as witnessed by the lithic records and the chronicles was due to the efforts of the Buddhist monks who spread Theravada or the orthodox tradition of the religion in the first few centuries. Its spread went parallel with the growth of monastic institutions in the island.
At first the patronage extended by the kings and the people towards the Buddhist monks was to safeguard the religion. They were endowed with dwellings and requisites for their maintenance. To make them self-sufficient the monks were endowed with permanent and valuable gifts consisting of land, tanks, revenue from taxes and so forth. When these endowments were made, the monks became landholders and gained a role of leadership in society. On the one hand, the relationship with the masses made the Sangha an institution which dominated society in its own way. On the other, it became a major factor to check the royal power.
The monks generally regarded themselves as having a two-fold task; striving for their own salvation and preaching the Dhamma to lead others to find their salvation. It was the scholar and the preacher in them that were useful to society.
Buddhism was flourishing in the entire island by the second century A.D. Even before that dissensions among members of the Sangha were visible in the premiere establishments such as Mahāvihara and Abhayagirivihära. Some individuals struggled for power and tried to gain favours from the kings. By about the third century A.D. new trends of thought in Buddhism, coming from the subcontinent of India were making headway in the island. By contact with these new movements, the monks of the Abhayagirivihara were becoming liberal in their views. The new schools of thought such as Vaitulyavāda, described as heresies in the chronicles, divided them into sects. These schools of new thought had the backing of some kings through the Mahāvihăra vehemently opposed them.
By about the fourth century, there were three fraternities, namely, Mahāvihāra, Abhayagiri, and Jetavana. The inscriptions and the chronicles bear clear evidence to the manifestation of Mahāyāna ideals such as the Bodhisattva worship. The sixth and seventh-century inscriptions attach great importance to the merit-making rituals that accompanied them. Here we find the Sangha in the role of the priest invoking blessings on the masses and becoming an indispensable figure in society.