Devotee: Prabhupāda? You said Arjuna was lamenting, but pure devotees become... superior qualities that all devotees possess... so why is this? So why did Kṛṣṇa call him a fool?
Prabhupāda: Yes. In spite of our superior qualities, we are always fool. You should know. Don't be puffed up with your superior qualities. You should remain always fool. Just like Caitanya Mahāprabhu, He presents Himself as a fool. So even Caitanya Mahāprabhu presents Himself before His spiritual master as a fool.
So that is a good qualification, to remain a fool. Otherwise, if he becomes puffed up—"Oh, I have learned everything. My business is finished"—so there is prone to fall down again. Arjuna was addressed as a fool, because Arjuna accepted Kṛṣṇa as his spiritual master. So the spiritual master has the right, just like father has the right to say like that. So there was nothing wrong.
(break) ...kīrtanaṁ viṣṇoḥ. This is chanting and hearing of the glories of Viṣṇu, harer nāma kīrtanam (CC Adi 17.21). So that is the beginning. Devotional service begins from hearing. Unless there is chanting, what you can hear? Śravaṇādi-śuddha-citte (CC Madhya 22.107). Śravaṇādi. Śravaṇa means hearing. That is the beginning of devotional... as you chant and hear, so you become purified more and more.
Then your heart becomes cleansed. Ceto-darpaṇa-mārjanam (CC Antya 20.12). The whole thing is that we have accumulated so many nasty things in our heart. That has to be moved. It is cleansing process. So chanting Hare Kṛṣṇa mantra means beginning the cleansing process. Ceto-darpaṇa-mārjanaṁ bhava-mahā-dāvāgni-nirvāpaṇam. Is it clear?
(Srila Prabhupada Lecture, Gorakhpur, February 18, 1971)