(Click to enlarge photo of Srila Prabhupada)
Devotee: Swāmījī, someone approached me, and we were discussing about Kṛṣṇa consciousness. And I said to approach Kṛṣṇa one must be pure, but he said, "What is purity?" Could you explain that technically? What is purity?
Prabhupāda: Yes. Purity means standing on the spiritual platform. That is purity. In the material platform there is no purity. So according to Bhagavad-gītā, that standard of purity, that means standing on the spiritual platform, which is called brahma-bhūtaḥ. Brahma-bhūtaḥ. So Kṛṣṇa says this purity,
māṁ ca vyabhicāreṇa
bhakti-yogena yaḥ sevate
sa guṇān samatītyaitān
This Brahman understanding, or to stand on the Brahman platform, is purity. How one can attain that platform of purity? Kṛṣṇa says that "One who is engaged in devotional service to Me without any deviation," that means twenty-four hours in Kṛṣṇa consciousness, "he is pure." He is pure. If you can keep yourself always, constantly, in Kṛṣṇa consciousness, always thinking of Kṛṣṇa, then you are pure. Otherwise... Kṛṣṇa consciousness or God consciousness, it doesn't make any difference.
So just like if you keep always in touch with fire you are warm—there is no possibility of being cold—similarly, some way or other if you always keep yourself in Kṛṣṇa consciousness or God consciousness, then you are pure. Therefore we advise our students, "Chant Hare Kṛṣṇa." As soon as you chant this sound, "Kṛṣṇa," immediately you are in touch with Kṛṣṇa. Therefore you are..., you keep yourself pure. Is that clear? Yes.
So try to keep yourself in Kṛṣṇa consciousness without any deviation. Then you remain pure. That is also confirmed in the Bhagavad-gītā, daivī hy eṣā guṇamayī... (BG 7.14). It is very difficult to get out of the clutches of this māyā, contamination. Very difficult. Mām eva ye prapadyante: "But one who keeps touch with Me, with full surrender," māyām etāṁ taranti te, "he's out of these clutches of māyā."
So just like there is antiseptic, what is called, vaccination, to keep yourself from the contamination... There is epidemic, and under government order everyone is vaccinated, that "You take this vac..., so you shall keep your..." This is material way of keeping oneself from contamination. Similarly, if you keep always yourself in spiritual understanding of Kṛṣṇa consciousness, you'll remain pure.
(Srila Prabhupada Lecture, Seattle, September 25, 1968)