Śrī Caitanya Mahāprabhu quotes this verse from the Adi Purāṇa. The verse is also included in the Laghu-bhāgavatāmṛta (2.6).
Those who are My direct devotees are actually not My devotees, but those who are the devotees of My servant are factually My devotees
Expressions researched:
"Those who are My direct devotees are actually not My devotees, but those who are the devotees of My servant are factually My devotees"
Sri Caitanya-caritamrta
CC Madhya-lila
“[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.’
“[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.’