The real question is, How can we remain unpolluted by material contamination while in the material world? It was Rūpa Gosvāmī who explained that we can remain uncontaminated while in the world if we simply make it our ambition to serve Kṛṣṇa. One may then justifiably ask, “How can I serve?” Obviously this is not simply a matter of meditation, which is just an activity of the mind, but of practical work. Love of Kṛṣṇa’s service can be attained only by working for Kṛṣṇa. In such work, we should leave no resource unused. Whatever is there, whatever we have, should be used for Kṛṣṇa. We can use everything: typewriters, automobiles, airplanes, missiles-anything. If we simply speak to people about Kṛṣṇa consciousness, we are also rendering service. If our minds, senses, speech, money and energies are thus engaged in the service of Kṛṣṇa, we cannot be considered to exist in material nature. By virtue of spiritual consciousness, or Kṛṣṇa consciousness, we transcend the platform of material nature. It is a fact that Kṛṣṇa, His expansions and His devotees-that is, those who work for Him-are not in material nature, although people with a poor fund of knowledge think that they are.
Ref >> Srila Prabhupada Vani.