瑜伽論記 15.258

15.258

答曰：若受報，即應一千劫受彼果，以色界入定，此定是生報感五百劫，之滿已前欲界業熟應復受果更五百劫，即應一千劫而受彼果耶？若即色界之定感彼生報時欲界業等一時受別報者，此欲界業便成生報，今時不受此果此業便於生未熟羸劣故。

The answer is: If it experienced retribution, one should experience that fruit for one thousand eons. Because one enters concentration in the form realm, this concentration is retribution upon rebirth inducing five hundred eons; when that is exhausted, the former desire-realm karma would mature and should experience fruit for another five hundred eons—should one then experience that fruit for one thousand eons? If, when the concentration of the form realm induces that retribution upon rebirth, the desire-realm karma, etc., simultaneously experienced a distinct retribution, then this desire-realm karma would become retribution upon rebirth; since it does not experience this fruit now, this karma is not yet mature and is feeble at rebirth.