The Lord Buddha mentioned this statement regarding to the following story. A jealous queen Magandiya, caused an innocent rival of hers, Samavati, to be burnt alive. The king, hearing of the pathetic incident, subjected Magandhiya to a worse death. The monks wished to know which of the two was actually alive and which was actually dead. The Buddha explained that the heedless, like Magandhiya, should be Samavati, should be regarded as alive. appamādō amatapadaṁ pamādō maccunō padaṁ appamattā na mīyanti ye pamattā yathā matā Quoted from: The Dhammapada
Get the light leaving darkness