Faith is attained by the discharge of devotional service, and by chanting "Hare Krsna, Hare Krsna, Krsna Krsna, Hare Hare, Hare Rama, Hare Rama, Rama Rama, Hare Hare," which cleanses one's heart of all material dirt. BG 1972 purports

Expressions researched:
"which cleanses one's heart of all material dirt"

Bhagavad-gita As it is

BG Chapters 1 - 6

One is called a faithful man who thinks that, simply by acting in Kṛṣṇa consciousness, he can attain the highest perfection. This faith is attained by the discharge of devotional service, and by chanting "Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare," which cleanses one's heart of all material dirt. Over and above this, one should control the senses. A person who is faithful to Kṛṣṇa and who controls the senses can easily attain perfection in the knowledge of Kṛṣṇa consciousness without delay.

BG 4.39 (1972), Translation and Purport

A faithful man who is absorbed in transcendental knowledge and who subdues his senses quickly attains the supreme spiritual peace.

Such knowledge in Kṛṣṇa consciousness can be achieved by a faithful person who believes firmly in Kṛṣṇa. One is called a faithful man who thinks that, simply by acting in Kṛṣṇa consciousness, he can attain the highest perfection. This faith is attained by the discharge of devotional service, and by chanting "Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare," which cleanses one's heart of all material dirt. Over and above this, one should control the senses. A person who is faithful to Kṛṣṇa and who controls the senses can easily attain perfection in the knowledge of Kṛṣṇa consciousness without delay.