瑜伽論記 6.374

6.374

六、因緣者，因請而說，即一切經律但是有請說者皆名因緣經。言及諸所有毘奈耶等者，十二年前眾未有犯但略教誡，十二年後因眾有犯廣說戒經名因緣經。

Sixth, 'narratives of origin' (nidāna): spoken on account of a request; that is, all sūtras and vinaya texts that are spoken because of a request are called nidāna sūtras. As for the statement 'and all vinaya and so forth', prior to twelve years, the community had no transgressions, so there were only brief admonitions; after twelve years, because members of the community committed transgressions, the precepts were expounded extensively, which are called nidāna sūtras.