諸經要集 12.60

12.60

又善見律云。佛言。龍有五事。不得離龍身。何者為五。一行婬時。若與龍共行婬。得復龍身。若與人共行婬。不得復龍身。二受生不離龍身。三脫皮時。四眠時。五死時。是為五事。不得離龍身。

Furthermore, the Samantapāsādikā states: The Buddha said: Nāgas have five situations in which they cannot be free from the nāga body. What are the five? First, when engaging in sexual intercourse: if engaging in intercourse with a nāga, they may remain in nāga body, but if engaging in intercourse with a human, they cannot be free from the nāga body. Second, at the time of taking rebirth, they are not free from the nāga body. Third, at the time of shedding skin. Fourth, when asleep. Fifth, at the time of death. These are the five situations in which they cannot be free from the nāga body.