Uposathasutta

Suttapiṭaka · Saṁyuttanikāya · Khandhavaggasaṁyutta · Vol. 17 · Section 521

[521] At Sāvatthī. Then a certain bhikkhu approached the Blessed One … Sitting to one side, that bhikkhu said this to the Blessed One: "Venerable sir, what is the cause, what is the condition, why some womb-born (jalābuja) nāgas here observe the uposatha and relinquish their bodies?" (All should be expanded in full.) "This, bhikkhu, is the cause, this is the condition, why some womb-born nāgas here observe the uposatha and relinquish their bodies."

English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.