Āsīvisasutta
“Cattārome, bhikkhave, āsīvisā. Katame cattāro? Āgataviso na ghoraviso, ghoraviso na āgataviso, āgataviso ca ghoraviso ca, nevāgataviso na ghoraviso— Ime kho, bhikkhave, cattāro āsīvisā. Evamevaṁ kho, bhikkhave, cattāro āsīvisūpamā puggalā santo saṁvijjamānā lokasmiṁ. Katame cattāro? Āgataviso na ghoraviso, ghoraviso na āgataviso, āgataviso ca ghoraviso ca, nevāgataviso na ghoraviso.
Vipers
“Mendicants, there are these four kinds of viper. What four? One whose venom is fast-acting but not lethal, one whose venom is lethal but not fast-acting, one whose venom is both fast-acting and lethal, and one whose venom is neither fast-acting nor lethal. These are the four kinds of viper. In the same way, these four individuals similar to vipers are found in the world. What four? One whose venom is fast-acting but not lethal, one whose venom is lethal but not fast-acting, one whose venom is both fast-acting and lethal, and one whose venom is neither fast-acting nor lethal.