CC Madhya 9.132
yathā bhakti-matām iha
na — not; ayam — this Lord Śrī Kṛṣṇa; sukha-āpaḥ — easily available; bhagavān — the Supreme Personality of Godhead; dehinām — for materialistic persons who have accepted the body as the self; gopikā-sutaḥ — the son of mother Yaśodā; jñāninām — for persons addicted to mental speculation; ca — and; ātma-bhūtānām — for persons performing severe austerities and penances; yathā — as; bhakti-matām — for persons engaged in spontaneous devotional service; iha — in this world.
Caitanya Mahāprabhu then quoted, “ ‘The Supreme Personality of Godhead, Kṛṣṇa, the son of mother Yaśodā, is accessible to those devotees engaged in spontaneous loving service, but He is not as easily accessible to mental speculators, to those striving for self-realization by severe austerities and penances, or to those who consider the body the same as the self.’
This verse, also given in Madhya-līlā 8.227, is quoted from Śrīmad-Bhāgavatam (10.9.21).