the Awakened One was residing at Sāvatthi
In Jeta’s grove, at Anāthapiṇḍika’s Monastery.
At that time in Sāvatthi,
A certain monk died from a snake bite. 
Many monks approached the Buddha;
Paid loving respects,
Sat down in front of him
And reported this.
This monk surely did not pervade
The four royal families of snakes with a loving mind. 
If he had done so monks,
That monk would not have died, bitten by a snake.”
What four? 
(1) The royal family of the Viperidae  snakes
(2) The royal family of the Elapid  snakes,
(3) The royal family of the Colubrid  snakes,
“Monks, this monk surely did not pervade
These four royal snake families with a loving mind.”
For your own safety,
Your own protection,
Your own security; 
I advise you to pervade
these four royal families of snakes
[In this way, thinking:]
‘I have love for the vipers
For the elapids I have love;
I have love for the colubrids,
For the black hydrophids I have love. 
I have love for those without feet,
For those with two feet I have love;
I have love for those with four feet,
For those with many feet I have love. 
Let those without feet not hurt me,
Let those with two feet not hurt me;
Let those with four feet not hurt me,
Let those with many feet not hurt me. 
May all beings, all who breath,
all the living and the rest;
May they all come upon well-being,
May no wrong come to them. 
Measureless is the Buddha,
Measureless is the Dhamma;
Measureless is the Saṅgha;
Creepings things are limited and measurable; 
Snakes, centipedes, Spiders, lizards and rats; 
I have made this protection,
I have made this safeguard,
May these beings turn away; 
As I pay homage to the Awakened One,
Homage to the seven Perfectly all-awakened Buddhas.’ 
 aññataro bhikkhu ahinā daṭṭho kālaṅkato hoti.
 “Na hi nūna so, bhikkhave, bhikkhu cattāri ahirājakulāni mettena cittena phari.
 Venomous snakes belong to four families Viperidae, Elapidae, Colubridae and Hydrophidae. (Journal of Venomous Animals and Toxins including Tropical Diseases On-line version ISSN 1678-9199)
 Virūpakkhaṃ: (Shapeshifter?) Viperidae: a widely distributed family comprising heavy-bodied venomous snakes that include Old World snakes (subfamily Viperinae) and the pit vipers (subfamily Crotalinae) and that are characterized by large tubular venom-conducting fangs erected by rotation of the movable premaxillae. (Merriam-webster)
 Erāpathaṃ: Elapid 1. any venomous snake of the mostly tropical family Elapidae, having fixed poison fangs at the front of the upper jaw and including the cobras, coral snakes, and mambas (Collins)
 Chabyāputtaṃ: (Six bad sons?) Colubrid, (?) any member of the most common family of snakes, Colubridae, characterized by the complete absence of hind limbs, the absence or considerable reduction of the left lung, and the lack of teeth on the premaxilla and usually having a loose facial structure, relatively few head scales, and ventral scales as wide as the body. (Britannica)
 Sea snake n. Any of various venomous aquatic snakes of the family Elapidae (or Hydrophiidae) that inhabit tropical waters of the Pacific and Indian Oceans and that bear live offspring. (Medical-dictionary)
 Virūpakkhaṃ ahirājakulaṃ, erāpathaṃ …, chabyāputtaṃ …, kaṇhāgotamakaṃ ….
 Anujānāmi, bhikkhave, imāni cattāri ahirājakulāni mettena cittena pharituṃ attaguttiyā attarakkhāya attaparittāyāti.
 Virūpakkhehi me mettaṃ, Mettaṃ erāpathehi me; Chabyāputtehi me mettaṃ, Mettaṃ kaṇhāgotamakehi ca.
 Apādakehi me mettaṃ, mettaṃ dvipādakehi me; Catuppadehi me mettaṃ, mettaṃ bahuppadehi me.
 Mā maṃ apādako hiṃsi, mā maṃ hiṃsi dvipādako; Mā maṃ catuppado hiṃsi, mā maṃ hiṃsi bahuppado.
 Sabbe sattā sabbe pāṇā, sabbe bhūtā ca kevalā; Sabbe bhadrāni passantu, mā kañci pāpamāgamā.
 Appamāṇo buddho, Appamāṇo dhammo; Appamāṇo saṃgho, Pamāṇavantāni sarīsapāni.
 Ahivicchikā satapadī, Uṇṇanābhī sarabū mūsikā;
 Katā me rakkhā katā me parittā, Paṭikkamantu bhūtāni;
 Sohaṃ namo bhagavato, Namo sattannaṃ sammāsambuddhānan”ti.