欲界三毒、色界二毒、无色界一毒

总而言之，欲界是三毒具足，色界有二毒，无色界有一毒，所以三界无非就是贪瞋痴。众生有这一些痛苦，有三毒之火，如来就是为了度化众生离开这一些痛苦、灭掉三毒之火，才要这么辛苦来受生于人间。来到人间之后就是教化众生来证得无上正等正觉，……。
《法华经讲义》第四辑，页295

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In short, the desire-realm is plagued by all three poisons, the form-realm by two poisons, and the formless-realm by one poison. In other words, the three realms are nothing but greed, aversion, and delusion. Seeing that all sentient beings are suffering from the fires of the three poisons, the Tathāgata has made the great sacrifice to be born in the human world in order to teach them how to stay away from the miseries and extinguish the fires of the three poisons. After he was born in the human world, he began to teach sentient beings the way to attain the fruition of the unsurpassed, complete and perfect enlightenment.
A Discourse on the Lotus Sutra, vol. 4, p. 295