俱舍論疏 28.182

28.182

論「如由加行至順退分定」，指事釋也。已成根本靜慮，更得少分順決擇分，由加行得，不由離染及生得也。離自地染失退分定，退自地染得退分定。此由退得，非離染得及生得也。若全不成而初得者，即下七地由二得也。若離下地染得上地定，若從上生下得下地定，非想無上地，故無生得也。

The passage of the śāstra from 'As through application...' down to '...the attainment conducive to degeneration' points to the concrete matter and explains it. Having already accomplished the fundamental dhyāna, one further acquires a fraction conducive to decisive penetration; this is acquired through application, not through detachment from defilement or rebirth. Detaching from the defilement of one's own stage, one loses the attainment conducive to degeneration; falling back into the defilement of one's own stage, one acquires the attainment conducive to degeneration. This is acquired through falling back, not through detachment from defilement or rebirth. If one is entirely unaccomplished and acquires it for the first time, then in the lower seven stages it is acquired through two causes: if one detaches from the defilement of a lower stage, one acquires the attainment of a higher stage; if one is reborn from an upper stage into a lower one, one acquires the attainment of the lower stage. The Sphere of Neither Conception Nor Non-conception has no higher stage, so it lacks acquisition through rebirth.