CC Madhya 22.105
bhāvā sā sādhanābhidhā
prākaṭyaṁ hṛdi sādhyatā
kṛti-sādhyā — which is to be executed by the senses; bhavet — should be; sādhya-bhāvā — by which love of Godhead is acquired; sā — that; sādhana-abhidhā — called sādhana-bhakti, or devotional service in practice; nitya-siddhasya — which is eternally present; bhāvasya — of love of Godhead; prākaṭyam — the awakening; hṛdi — in the heart; sādhyatā — potentiality.
“ ‘When transcendental devotional service, by which love for Kṛṣṇa is attained, is executed by the senses, it is called sādhana-bhakti, or the regulative discharge of devotional service. Such devotion eternally exists within the heart of every living entity. The awakening of this eternal devotion is the potentiality of devotional service in practice.’
This verse is found in the Bhakti-rasāmṛta-sindhu (1.2.2). Because living entities are minute, atomic parts and parcels of the Lord, devotional service is already present within them in a dormant condition. Devotional service begins with śravaṇaṁ kīrtanam, hearing and chanting. When a man is sleeping, he can be awakened by sound vibration; therefore every conditioned soul should be given the chance to hear the Hare Kṛṣṇa mantra chanted by a pure Vaiṣṇava. One who hears the Hare Kṛṣṇa mantra thus vibrated is awakened to spiritual consciousness, or Kṛṣṇa consciousness. In this way one’s mind gradually becomes purified, as stated by Śrī Caitanya Mahāprabhu (ceto-darpaṇa-mārjanam). When the mind is purified, the senses are also purified. Instead of using the senses for sense gratification, the awakened devotee employs the senses in the transcendental loving service of the Lord. This is the process by which dormant love for Kṛṣṇa is awakened.