The tradition has ancient roots. Bhakti is mentioned in the Shvetashvatara Upanishad where it simply means participation, devotion and love for any endeavor.[3][4] Bhakti yoga as one of three spiritual paths for salvation is discussed in depth by the Bhagavad Gita.[5][6][7]
The bhakti marga involving these deities grew with the bhakti movement, starting about the mid-1st millennium CE, from Tamil Nadu in South India. The movement was led by the Saiva Nayanars[10] and the Vaisnava Alvars. Their ideas and practices inspired bhakti poetry and devotion throughout India over the 12th-18th century CE.[11][10] Bhakti marga is a part of the religious practice in Vaishnavism, Shaivism, and Shaktism.[12][13][14]
^Karen Pechelis (2014), The Embodiment of Bhakti, Oxford University Press, ISBN978-0195351903, pages 19-24
^John Lochtefeld (2014), The Illustrated Encyclopedia of Hinduism, Rosen Publishing New York, ISBN978-0823922871, pages 98-100, also see articles on bhaktimārga and jnanamārga