俱舍論記 29.62

29.62

「論曰至皆增盛故」者，此即總釋。生上二界，總由三緣起二界定。一由因力，謂於先時隨在何界，前生近起及數修習，為今現起同類因故。二由業力，謂先曾造感上地生順後受業，業果將現前，勢力令起定，以必離下方生上故。三法爾力，世界將壞，法爾能得上界定故。

"The treatise says: [...] because all flourish": this is the general explanation. Those born in the upper two realms generally give rise to the absorptions of the two realms through three conditions. First, through the power of a cause: that is, at an earlier time, in whichever realm one was in, proximate origination and repeated cultivation in a previous life serve as the homogeneous cause for their present active arising. Second, through the power of karma: that is, having previously created karma to be experienced in subsequent lives that induces birth in a higher stage, when the karmic fruit is about to manifest, its force causes the absorption to arise, because one must be detached from the lower to be born in the upper. Third, the power of natural order: when the world is about to be destroyed, by natural order one can attain the absorptions of the higher realms.