金光明最勝王經疏 2.429

2.429

贊曰：解應化身不住所以，初順解、次返成。一假名非實、二念念生滅、三數數出現。出現者，為眾生故，或時現入滅、或時受生，故數數出現。以不定故者，明不住涅槃。

The commentary says: This explains the reason why the response and transformation bodies do not abide, first explaining directly, and next establishing by converse. First, nominal and not real; second, arising and ceasing thought-moment by thought-moment; third, appearing again and again. 'Appearing' means: for the sake of sentient beings, sometimes manifesting entry into cessation, sometimes undergoing birth; therefore, appearing again and again. 'Because of being non-fixed' explains not abiding in nirvāṇa.