(Mv.I.63.1) [127] Now at that time a certain nāga was horrified, humiliated, and disgusted with his nāga-birth. Then the thought occurred to him: “Now, by what strategy might I be freed from the nāga-birth and quickly regain the human state?”

Then he thought, “These Sakyan-son contemplatives live in line with the Dhamma, live in tune, live the holy life, speak the truth, are virtuous and fine-natured.

“If I went forth among the Sakyan-son contemplatives, I would thus be freed from the nāga-birth and quickly regain the human state.”

(Mv.I.63.2) So, in the form of a brahman youth, he went to the monks and requested the Going-forth. The monks gave him the Going-forth; they gave him Acceptance. Now at that time the nāga lived together with a certain monk in a dwelling on the perimeter (of the monastery). Then the monk, getting up in the last watch of the night, walked back and forth in the open air. The nāga, when the monk had left, fell asleep with his guard down. The entire dwelling was filled with snake. Coils were coming out through the windows.

(Mv.I.63.3) Then the monk, (thinking,) “I’ll enter the dwelling,” and opening the door, saw the entire dwelling filled with snake and the coils coming out through the windows. On seeing this, frightened, he let out a shriek. Monks came running and said to him, “Why, friend, did you let out a shriek?”

“This entire dwelling, friends, is filled with snake! Coils are coming out through the windows!”

Then the nāga, having awakened at the noise, sat in his own seat. The monks said, “Who are you, friend?”

“I am a nāga, venerable sirs.”

“But why, friend, did you do such a thing?”

Then the nāga reported the matter to the monks. The monks reported the matter to the Blessed One.

(Mv.I.63.4) Then the Blessed One, with regard to this cause, to this incident, had the Saṅgha of monks assembled and said to the nāga:

“You nāgas are not liable to growth in this Dhamma and discipline. Go, nāga. (Staying) right there[2], observe the uposatha on the fourteenth (or) fifteenth and eighth of the fortnight. Thus you will be freed from the nāga-birth and quickly regain the human state.”

The nāga, (thinking,) “It’s said that I’m not liable to growth in this Dhamma and discipline!” sad and unhappy, shedding tears, let out a shriek and left.

(Mv.I.63.5) Then the Blessed One addressed the monks, “Monks, there are two conditions for a male nāga’s reverting to his own state: when he engages in intercourse with a female of his own species, and when he falls asleep with his guard down. These are the two conditions for a male nāga’s reverting to his own state.”

“Monks, an animal, if unaccepted, is not to be given Acceptance. If accepted, he is to be expelled.”