The Bodhisatta was once born in Kāsi, and later became an ascetic. On it being reported to him that many ascetics died of snake-bite, he gathered them together and taught them how, by cultivating love for the four royal races of snakes -
the Virūpakkhas,
the Erāpattas,
the Chabbyāputtas, and
the Kanhagotamas -
they could prevent themselves from ever being bitten by any creature.
The story was told in reference to a monk who died of snake-bite. J.ii.144ff.. cf. Vin.ii.109f.
The story is evidently an expansion of the Khanda Paritta.