大般涅槃經集解 56.108

56.108

案僧亮曰：觀緣具不退，不具則退也。僧宗曰：明以遲得故言退，非為永失也。寶亮曰：正辨不退之由也。

Sengliang states: If he contemplates with conditions complete, he does not retrogress; if incomplete, he retrogresses. Sengzong states: He explains that because of late attainment it is called retrogression, not that it is permanently lost. Baoliang states: He directly discerns the reason for non-retrogression.