SB 6.9.39
atha ha vava tava mahimamrta-rasa-samudra-viprusa sakrd avalidhaya sva-manasi nisyandamananavarata-sukhena vismarita-drsta-sruta-visaya-sukha-lesabhasah parama-bhagavata ekantino bhagavati sarva-bhuta-priya-suhrdi sarvatmani nitaram nirantaram nirvrta-manasah katham u ha va ete madhumathana punah svartha-kusala hy atma-priya-suhrdah sadhavas tvac-caranambujanusevam visrjanti na yatra punar ayam samsara-paryavartah.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Therefore, O killer of the Madhu demon, incessant transcendental bliss flows in the minds of those who have even once tasted but a drop of the nectar from the ocean of Your glories. Such exalted devotees forget the tiny reflection of so-called material happiness produced from the material senses of sight and sound. Free from all desires, such devotees are the real friends of all living entities. Offering their minds unto You and enjoying transcendental bliss, they are expert in achieving the real goal of life. O Lord, You are the soul and dear friend of such devotees, who never need return to this material world. How could they give up engagement in Your devotional service?
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Although nondevotees, because of their meager knowledge and speculative habits, cannot understand the real nature of the Lord, a devotee who has once tasted the nectar from the Lord’s lotus feet can realize what transcendental pleasure there is in the Lord’s devotional service. A devotee knows that simply by rendering service to the Lord, he serves everyone. Therefore devotees are real friends to all living entities. Only a pure devotee can preach the glories of the Lord for the benefit of all conditioned souls.