唯識二十論述記 1.182

1.182

述曰：釋初句頌，若龍麟等，生天上者，唯在欲界地居天中，其鶴鳳等亦通欲界空居天有。此等必有共業，是善能感彼天外器樂業，既有果生故，能受彼器所生樂，此顯他宗同喻差別，下成彼宗法之差別。

The Commentary says: Explaining the first line of the verse: as for dragons, unicorns, and the like born in heaven, they exist only among the terrestrial devas of the desire realm; while cranes, phoenixes, and the like also exist among the celestial devas of the desire realm. These beings necessarily possess collective karma, which is wholesome and capable of bringing about the pleasure of that external receptacle-world of the heavens; since the fruit is born, they can experience the pleasures produced by that receptacle-world. This demonstrates the distinction in the similar example of the other school; below establishes the distinction in the property of that school.