CC Madhya-lila 11.028 - Adi Purana
Sri Caitanya-caritamrta
CC Madhya-lila
CC Madhya 11.28, Translation and Purport:
“(Lord Kṛṣṇa told Arjuna:) "Those who are My direct devotees are actually not My devotees, but those who are the devotees of My servant are factually My devotees."
Śrī Caitanya Mahāprabhu quotes this verse from the Ādi Purāṇa. The verse is also included in the Laghu-bhāgavatāmṛta (2.6).