SB 3.32.37

The process of bhakti-yoga, devotional service, is the main river flowing down towards the sea of the Absolute Truth, and all other processes mentioned, they are just like tributaries to the process of devotional service. Therefore, Lord Kapila is summarizing about the importance of the process of devotional service. Such bhakti-yoga, as described before, divided into four divisions-three in the material modes of nature and one in transcendence without any tinge of the modes of material nature. Devotional service mixed with the three modes of material nature is meant for material existence, whereas the transcendental devotional service or pure devotional service without any desire for fruitive result or without any attempt for empiric philosophical research, that is pure devotional service and transcendental.