大般涅槃經疏 28.29

28.29

「以是因緣」下，第二十犯四重人有佛性無佛性。開善云：二十者，此還屬第十九佛性即離之義。若冶城云二十一，此是第二十，何故屬前？前云即眾生離眾生，此中云作五逆犯重佛性有無，云何是同？故為異。

From "Because of these causes and conditions" below, the twentieth is whether a person who has committed the four grave offenses has the buddhadhātu or does not have the buddhadhātu. Kāishàn says: as the twentieth, this still belongs to the nineteenth topic on the meaning of the buddhadhātu being identical or apart. If according to Yěchéng, there are twenty-one, this being the twentieth; why should it belong to the preceding? The preceding says identical to sentient beings or apart from sentient beings; here it discusses whether one who commits the five heinous acts and violates the grave offenses has the buddhadhātu or not—how are they the same? Therefore, they are distinct.