In Nārada Pañcarātra it is recommended . . . we are explaining these things in Devotional . . . Nectar of Devotion. The basic principle of purification is smartavyaḥ satato viṣṇuḥ, always one has to remember Viṣṇu or Kṛṣṇa. Kṛṣṇa and Viṣṇu the same. When you speak Kṛṣṇa, it includes Viṣṇu. So smartavyaḥ satato viṣṇu vismartavyaḥ na jātucit.
We shall not forget Viṣṇu even for a moment. This is the basic principle of devotional life. Some way or other, we have to remember always Kṛṣṇa. Then whatever condition we may be, we are pure. Sa bahyābhyantaraṁ śuciḥ. This chanting helps us always remembering Kṛṣṇa. As soon as we chant Hare Kṛṣṇa, hear, immediately we remember.
So, so long I remember, I am śuciḥ, I am pure, no material contamination. Therefore if I continue my life in that pure stage, then I am eligible for going back to Godhead. Because nobody can enter in the kingdom of God without being completely pure. Completely pure means anyābhilāṣitā-śūnyam (Bhakti-rasāmṛta-sindhu 1.1.11), no material desire. Here in the material world, we manufacture so many plans to be happy, material desires. Somebody's thinking, "I shall be happy in this way." Somebody's thinking . . . "There is no question of happiness here". The place is contaminated. In a contaminated . . . just like in an infected place you cannot be happy. The medical officer will ask you to leave that place that, "This quarter has been infected by the disease. Better you leave, you go somewhere else." That is the treatment. Infected place must be left immediately.