"Ecstatic love for Kṛṣṇa (prema) is described in the Bhakti-rasāmṛta-sindhu (1.41) as follows:
bhāvaḥ sa eva sāndrātmā
budhaiḥ premā nigadyate
'When the heart is completely softened and devoid of all material desires and when one's emotional feelings become very strong, one becomes very much attached to Kṛṣṇa. Such purified emotion is known as pure love.' "