俱舍論記 24.62

24.62

「經生習根至所依止故」者，釋。經生習根極成熟故，及得殊勝所依身故。昔是凡身未名殊勝，經生聖者唯是聖身方名殊勝，或上界身亦名殊勝，由此彼無練根、退理。又解：經生習根極成熟故，顯無練根。及得殊勝所依止故，顯無退也。應知欲界唯人趣退，三惡趣中無聖道退。天趣雖有，彼無退具功德堅牢，設不經生亦不退也。

Regarding [the text from] “Because having undergone rebirth, the cultivated faculties [...]” to “[...] basis,” this is the explanation. It is because having undergone rebirth, the cultivated faculties are extremely mature, and because they have attained a superior basis [of body]. Formerly it was an ordinary person’s body, which was not called superior; for a noble person who has undergone rebirth, it is exclusively a noble body, and only then is called superior; or a body of the higher realm is also called superior. Therefore, for them, there is no principle of refinement of faculties or falling away. Another explanation: “because having undergone rebirth, the cultivated faculties are extremely mature” indicates the absence of refinement of faculties; and “having attained a superior basis” indicates the absence of falling away. One should know that in the desire realm, only the human destiny has falling away; among the three bad destinies, there is no falling away from the noble path. Although it exists in the deva destiny, they lack the causes for falling away and their virtues are firm; even if they have not undergone rebirth, they do not fall away either.