The Mahavagga (Vinaya Pitaka)

The Mahavagga, part of the Khandhaka division of the Pali Vinaya Pitaka, is the Buddhist monastic code's own text governing the early sangha's formation, including the procedures for ordination, the rules for the rains retreat and the account of the Buddha's own first teachings and early converts. Its strength is that it is a primary canonical text itself, the Theravada tradition's own foundational record of how monastic life and discipline were established, rather than a later commentator's account of it. Its limit is that, like the rest of the Pali canon, the Mahavagga was transmitted orally for generations before being committed to writing, so its narrative episodes, while foundational to Theravada self-understanding, are not independently verifiable historical record in the way a contemporary document would be, and a claim treating a specific narrative detail as established history rather than canonical tradition should say so.