《中部》第七經，以髒布難以染色為喻，說明心懷染汙者難得安樂，並闡明真正的淨化在於清淨內心而非儀式性沐浴。

The seventh sutta of the Majjhimanikāya, teaching through the simile of a dirty cloth that fails to take dye well that a heart burdened with impurities cannot find happiness, and describing true purification as cleansing of the heart rather than ritual bathing.