成唯識論述記 8.461

8.461

述曰：此第七問。從上生下，從下生上，彼所能潤當生之愛，取其何地受支為緣？為當生地？為現居地？何意有此問？既受緣愛，現起受支與當生愛異地故，應如無明發行，許異地成，為此問也。

The Commentary states: This is the seventh question. When reborn from a higher stage into a lower stage, or from a lower stage into a higher stage, taking the feeling branch of which stage as condition does that craving which is capable of moistening the future birth arise? Is it the stage of future birth, or the stage of present dwelling? What is the intent of having this question? Since feeling conditions craving, and the currently active feeling branch belongs to a different stage than the craving of future birth, it should be like ignorance initiating karmic formations, admitting establishment across different stages; hence this question is asked.