四分比丘戒本疏 1.8

1.8

Third, the piṭaka and vehicle under which it is subsumed: among the three piṭakas, it is subsumed under the Vinaya; among the three vehicles, since it is studied in common by all, it is universally subsumed under the three vehicles, because the moral discipline of the prātimokṣa is subsumed under the threefold pure precepts.