CC Madhya 21.83
kiṁ bahūktyā na me prabho
manaso vapuṣo vāco
vaibhavaṁ tava gocaraḥ
jānantaḥ — persons who think they are aware of Your unlimited potency; eva — certainly; jānantu — let them think like that; kim — what is the use; bahu-uktyā — with many words; na — not; me — my; prabho — O my Lord; manasaḥ — of the mind; vapuṣaḥ — of the body; vācaḥ — of the words; vaibhavam — opulences; tava — Your; gocaraḥ — within the range.
“ ‘There are people who say, “I know everything about Kṛṣṇa.” Let them think in that way. As far as I am concerned, I do not wish to speak very much about this matter. O my Lord, let me say this much. As far as Your opulences are concerned, they are all beyond the reach of my mind, body and words.’
This is a quotation from Śrīmad-Bhāgavatam (10.14.38), spoken by Lord Brahmā.