A Buddhist holy day is celebrated to acknowledge the end of the three month retreat undertaken by monks on Asalha Day sometimes called "Buddhist Lent".
It is celebrated on Aashvin full moon of the lunar month. According to legend, monks who were to spend three month together in the pursuit of meditative progress
felt it would be best to spend this time in silence to ensure minimal conflict and amicable co-existence during this time.
The Buddha discouraged the notion upon hearing of it, suggesting instead that an open minded sharing of ideas would result in the creation of a much stronger community. Thus began the tradition of discussing the perils and boons of monastic life and the knowledge obtained during the course of the last three months, on Pavarana Day, which comes some time between October and November.
Origin of Pavarana Day - In India, where Buddhism began, there is a three-month-long rainy season. According to the Vinaya (Mahavagga, Fourth Khandhaka, section I), in the time of the Buddha, once during this rainy season, a group of normally wandering monks sought shelter by co-habituating in a residence. In order to minimize potential inter-personal strife while co-habituating, the monks agreed to remain silent for the entire three months and agreed upon a non-verbal means for sharing alms.
After this rains retreat, when the Buddha learned of the monks' silence, he described such a measure as "foolish." Instead, the Buddha instituted the Pavarana Ceremony as a means for dealing with potential conflict and breaches of disciplinary rules (Patimokkha) during the Vassa season
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