SB 10.5.4
kalena snana-saucabhyam
samskarais tapasejyaya
sudhyanti danaih santustya
dravyany atmatma-vidyaya
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O King, by the passing of time, land and other material possessions are purified; by bathing, the body is purified; and by being cleansed, unclean things are purified. By purificatory ceremonies, birth is purified; by austerity, the senses are purified; and by worship and charity offered to the brahmanas, material possessions are purified. By satisfaction, the mind is purified; and by self-realization, or Krsna consciousness, the soul is purified.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
These are sastric injunctions concerning how one can purify everything according to Vedic civilization. Unless purified, anything we use will infect us with contamination. In India five thousand years ago, even in the villages such as that of Nanda Maharaja, people knew know to purify things, and thus they enjoyed even material life without contamination.