大般涅槃經集解 68.24

68.24

案僧亮曰：次答後問。言欲界受生是苦地，猶須外依資報身得立。然即用此為迫惱緣，故到來觀欲界為發悟之由，所以欲界有中陰。上界是禪地，不待外資，又無大苦，故無有中涅槃也。

Sengliang states: Next, he answers the latter question. It means taking birth in the desire realm is a realm of suffering, still requiring external reliance to support and sustain the retribution body. However, precisely by using this as a condition of pressing affliction, coming here and contemplating the desire realm serves as the cause of awakening; therefore, the desire realm has an intermediate state. The higher realm is a realm of dhyāna; it does not depend on external support, nor does it have great suffering, so it does not have intermediate nirvāṇa.