The Śūraṅgama Sūtra, Volume Five: Upāli among the Twenty-five Saints' Dharma Gates of Perfect Penetration

Original text:优波离。即从座起。顶礼佛足。而白佛言。我亲随佛。逾城出家。亲观如来六年勤苦。亲见如来降伏诸魔。制诸外道。解脱世间贪欲诸漏。承佛教戒。如是乃至三千威仪。八万微细。性业遮业。悉皆清净。身心寂灭。成阿罗汉。我是如来众中纲纪。亲印我心。持戒修身。众推无上。佛问圆通。我以执身。身得自在。次第执心。心得通达。然后身心。一切通利。斯为第一。

Explanation: Upāli rose from his seat, paid homage at the Buddha's feet, and replied to the Buddha: "I personally followed the Buddha, climbing over the city wall at midnight to leave home and cultivate the path in the Snow Mountains. With my own eyes I witnessed the Tathāgata's six years of arduous cultivation; I personally saw the Tathāgata subdue all māras and obstacles, subjugate all non-Buddhist paths, and become liberated from the afflictive outflows of various cravings for the world. I received the precepts taught by the Buddha and strictly observed them, down to the three thousand subtle practices of pure conduct (brahmacarya) that monastics should fully possess, the eighty thousand subtle afflictions, the unwholesome karmic actions of the mind-nature, and the obstructions from karmic seeds of actions created in past lives—all were completely eliminated. My mind attained purity, my body and mind reached quiescence and cessation, and I became an arhat.

Among the Tathāgata's assembly of bhikṣus, I was foremost in upholding the precepts, a model and exemplar of the bhikṣu precepts. The Buddha personally certified the purity of my body and mind, and in upholding the precepts and cultivating the self, the assembly esteemed me as foremost. Now the Buddha asks about the gateway to perfect penetration: it was because I first restrained the body that the material body attained freedom, never violating any of the bhikṣu precepts of deportment under any circumstances. After restraining bodily actions, I then progressively restrained mental actions, and thus the mind became thoroughly versed in the world of the five aggregates. Finally, my body and mind became completely unobstructed with respect to all dharmas in the world. I took upholding the precepts and cultivating body and mind as my foremost gateway to perfect penetration."

During the true Dharma age when the Buddha was in the world, one could attain realization simply by perfecting the precepts, up to becoming an arhat of the fourth fruit. In the Dharma-ending age, because sentient beings' spiritual faculties are deficient and their living environments are defiled, upholding the precepts alone can no longer lead to realization; one must cultivate precepts, meditation, and wisdom together, and only when all are perfected can realization be attained. If one does not observe the precepts, realization is even more impossible. When the mind-ground is turbid and impure, meditative concentration and wisdom cannot arise.