ananya-mamatā viṣṇau
mamatā prema-saṅgatā
bhaktir ity ucyate bhīṣma-
prahlādoddhava-nāradaiḥ
ananya-mamatā - having a sense of relationships with no others; viṣṇau - in Lord Viṣṇu, or Kṛṣṇa; mamatā - the sense of ownership; prema-saṅgatā - endowed only with love; bhaktiḥ - devotional service; iti - thus; ucyate - is said; bhīṣma - by Bhīṣma; prahlāda - by Prahlāda Mahārāja; uddhava - by Uddhava; nāradaiḥ - and by Nārada.
This verse, quoted from the Nārada-pañcarātra, is found in the Bhakti-rasāmṛta-sindhu (1.4.2).