This paper clarifies the sectarian affiliation of the fourteenth sūtra contained in the Dabaoji jing大宝積経 （Mahāratnakūṭa-sūtra）. The sūtra, Foshuo Rutaizang hui仏説入胎蔵会, tells the story of the conversion of Nanda, who is not able to concentrate on his practice because of his attachment to his wife, Sundarī. Using skillful means, the Buddha instructs Nanda and leads him to enlightenment. The sūtra contains several stories of the past in explanation of the circumstances of Nanda’s present life （for instance, to explain why he was born handsome）. Although sectarian identification of Mahāyāna sūtras is a controversial topic, close reading of the Rutaizang hui reveals some set expressions unique to the Sarvāstivādins, namely （1） the stanza on karma introducing a story of the past, （2） the description of a prosperous kingdom, （3） the description of a Pratyekabuddha, and （4） the Buddha’s instruction concerning karma which may be purely black, purely white, or mixed. These four set expressions clearly show that this version of the sūtra is affiliated with the Sarvāstivādins, a conclusion bolstered by the existence of a parallel found in the Mūlasarvāstivāda vinaya’s Kṣudraka-vastu.
