At Sāvatthī.

“Mendicants, dragons reproduce in these four ways. What four? Dragons are born from an egg, from a womb, from moisture, or spontaneously. Of these, dragons born from a womb, from moisture, or spontaneously are better than those born from an egg. Dragons born from moisture or spontaneously are better than those born from an egg or from a womb. Dragons born spontaneously are better than those born from an egg, from a womb, or from moisture. These are the four ways that dragons reproduce.”