Vatthasutta 12.2

12.2

Seyyathāpi, bhikkhave, vatthaṃ saṅkiliṭṭhaṃ malaggahitaṃ acchodakaṃ āgamma parisuddhaṃ hoti pariyodātaṃ, ukkāmukhaṃ vā panāgamma jātarūpaṃ parisuddhaṃ hoti pariyodātaṃ;

Compare with cloth that is dirty and soiled; it can be made pure and clean by pure water. Or native gold, which can be made pure and bright by a forge.