CC Madhya 18.111

prabhu kahe, — ‘viṣṇu’ ‘viṣṇu’ ihā nā kahibā!
jīvādhame ‘kṛṣṇa’-jñāna kabhu nā karibā!
Word for word: 
prabhu kahe — Śrī Caitanya Mahāprabhu replied; viṣṇu viṣṇu — “O Viṣṇu, Viṣṇu”; ihā — this; kahibā — do not speak; jīva-adhame — fallen conditioned souls; kṛṣṇa-jñāna — accepting as Lord Kṛṣṇa; kabhu — ever; karibā — do not do.
Translation: 
Śrī Caitanya Mahāprabhu immediately exclaimed, “Viṣṇu! Viṣṇu! Do not call Me the Supreme Personality of Godhead. A jīva cannot become Kṛṣṇa at any time. Do not even say such a thing!
Purport: 

Śrī Caitanya Mahāprabhu immediately stated that a living being, however exalted he may be, should never be compared to the Supreme Personality of Godhead. All of Śrī Caitanya Mahāprabhu’s preaching protests the monistic philosophy of the Māyāvāda school. The central point of Kṛṣṇa consciousness is that the jīva, the living entity, can never be accepted as Kṛṣṇa or Viṣṇu. This viewpoint is elaborated in the following verses.