CC Madhya 21.119
ihā haite mādhurya durlabha
kevala ye rāga-mārge, bhaje kṛṣṇe anurāge,
tāre kṛṣṇa-mādhurya sulabha
karma — fruitive activities; tapa — austerities; yoga — the practice of mystic yoga; jñāna — speculative cultivation of knowledge; vidhi-bhakti — regulative principles in devotional service; japa — chanting; dhyāna — meditation; ihā haite — from these things; mādhurya — the sweetness of Kṛṣṇa; durlabha — very difficult to perceive; kevala — only; ye — one who; rāga-mārge — by the path of spontaneous ecstatic love; bhaje — worships; kṛṣṇe — Lord Kṛṣṇa; anurāge — with transcendental feeling; tāre — unto him; kṛṣṇa-mādhurya — the sweetness of Kṛṣṇa’s; sulabha — very easily appreciated.
“The transcendental mellows generated from the dealings between the gopīs and Kṛṣṇa cannot be tasted by means of fruitive activity, yogic austerities, speculative knowledge, regulative devotional service, mantra-yoga or meditation. This sweetness can be tasted only through the spontaneous love of liberated persons who chant the holy names with great ecstatic love.