Dhamma Verses (Dhammapada, KN 2)

18: The Chapter about Stains – 219
The gradual purification
A brahmin saw the monks waiting to go for alms, and each day
improved the conditions where they gathered, until eventually
he built a hall for them, and invited the Buddha and the monks
for a meal; when the Buddha heard of his endeavours he spoke
this verse.
239. Anupubbena medhāvī, thokathokaṁ khaṇe khaṇe,
kammāro rajatasseva, niddhame malam-attano.
The sage gradually, gradually,
little by little, moment by moment,
should surely remove the stain from himself,
like a smith removes the stain from silver.