Saṁyutta Nikāya:
III. Khandhā Vagga:
29: Nāga Saṁutta
Kindred Sayings on Nāgas
Sutta 3
Uposatha Suttaṁ
Sabbath
Thus have I heard:
The Exalted One was once staying near Sāvatthī
at the Jeta Grove in Anāthapiṇḍika's Park.
Then a certain brother came to the Exalted One, and saluting [193] him
sat down at one side.
So seated that brother thus addressed the Exalted One:
"What is the reason, lord,
what is the cause
why some egg-born nāgas keep the Sabbath
and divest themselves of their nāga-forms?"1
"Herein, brother, certain egg-born nāgas think thus:
'Formerly we were double-dealing in speech,
double-dealing in act,
double-dealing in thought.
Thus in three ways being double-dealers,
when body breaks up after death
we shall be reborn in the company of egg-born nāgas.
Now if we were to practise virtuous deeds,
virtuous words
and virtuous thoughts,
when body breaks up after death
we might be reborn in the happy state,
in the heaven world.
Come now,
let us practise virtuous deeds,
virtuous words
and virtuous thoughts.'
This, brethren, is the reason,
this is the cause
why certain egg-born nāgas
keep the Sabbath
and divest themselves of their nāga-forms."
1 Vossaṭṭha-kāyā bhavanti. Cf. Jātaka iv, 460 (Campeyya-jātaka).