Barsabas a kind of educational retreat of Buddhist monks, undertaken for introspection and the performance of devotional rites. It has been in practice since the days of Buddha, who introduced it at Rajgriha. The rites are aimed at protecting plant life. While walking along rain-soaked and muddy pathways, one is likely to trample on green grasses, young plants and tiny creatures. This is why Buddha ordained that monks avoid traveling during the rainy season as much as possible and remain at their own viharas. He himself fixed a three-month period for barsabas - from asadhi purnima to Ashvini purnima. If sickness precludes a monk from undertaking barsabas at Asadhi purnima, he can undertake it from madhu purnima (Bhadra purnima) to Kartik purnima, also a three-month period.
During barsabas, monks perform various religious rites on every astami (eighth day of the lunar fortnight), amavasya (the last day of the lunar month), and purnima or full moon. They fast on these days and also visit families to talk to them about religious practices and rites.
During barsabas, Buddhists take vows of meditation, intense contemplation, and learning. Non-monks also join monks in performing religious rites. Every monk is required to perform monsoon rites on penalty of committing a grave sin.
Barsabas, prabarana and kathin chivar dan are all inter-related festivals. Without barsabas no monk can accept kathin chibar dan. The seniority of monks is determined by counting their barsabas. [Sukomal Barua]