Thus have I heard:

On one occasion the Blessed One was living near Savatthi at Jetavana at Anathapindika's monastery. At that time at Savatthi a certain monk had died bitten by a snake. Thereupon many monks approached the Buddha and having saluted him sat beside him. So seated those monks spoke thus to the Blessed One:

"Bhante (Venerable Sir), a certain monk at Savatthi had died bitten by a snake."

"Assuredly, monks," said the Buddha. "That monk has not suffused with thoughts of loving-kindness (metta) the four royal tribes of snakes. Had he done so, that monk would not have died of snake-bite. What are the four royal tribes of snakes? The royal tribe of snakes called Virupakkha, Erapatha, Chabyaputta, and Kanhagotamaka. Monks, that monk, did not suffuse with thoughts of loving-kindness these four royal tribes of snakes, had not done so he would not have died of snake-bite. Monks, I enjoin you to suffuse with thoughts of loving-kindness these four royal tribes of snakes for your safety, for your preservation and for your protection." So said the Blessed One. Having thus spoken, the Buddha, the "Welcome One" (Sugata), further said (suggesting how they should express themselves:)

"Infinite (in virtue) is the Buddha, infinite is the Dhamma, infinite is the Sangha. Finite are creeping creatures — snakes, scorpions, centipedes, spiders, lizards, and rats. I have guarded myself, I have made my protection. Depart from me, ye beings. I bow down to the Blessed One; and to the seven Supreme Buddhas." [1]