SB 3.9.1

brahmovāca
jñāto ’si me ’dya sucirān nanu deha-bhājāṁ
 na jñāyate bhagavato gatir ity avadyam
nānyat tvad asti bhagavann api tan na śuddhaṁ
 māyā-guṇa-vyatikarād yad urur vibhāsi
Synonyms: 
brahmā uvāca — Lord Brahmā said; jñātaḥ — known; asi — You are; me — by me; adya — today; sucirāt — after a long time; nanu — but; deha-bhājām — of one who has a material body; na — not; jñāyate — is known; bhagavataḥ — of the Personality of Godhead; gatiḥ — course; iti — so it is; avadyam — great offense; na anyat — none beyond; tvat — You; asti — there is; bhagavan — O my Lord; api — even though there is; tat — anything that may be; na — never; śuddham — absolute; māyā — material energy; guṇa-vyatikarāt — because of the mixture of the modes of; yat — to which; uruḥ — transcendental; vibhāsi — You are.
Translation: 
Lord Brahmā said: O my Lord, today, after many, many years of penance, I have come to know about You. Oh, how unfortunate the embodied living entities are that they are unable to know Your personality! My Lord, You are the only knowable object because there is nothing supreme beyond You. If there is anything supposedly superior to You, it is not the Absolute. You exist as the Supreme by exhibiting the creative energy of matter.
Purport: 

The highest peak of the ignorance of the living entities who are conditioned by material bodies is that they are unaware of the supreme cause of the cosmic manifestation. Different people have different theories regarding the supreme cause, but none of them are genuine. The only supreme cause is Viṣṇu, and the intervening impediment is the illusory energy of the Lord. The Lord has employed His wonderful material energy in manifesting many, many wonderful distractions in the material world, and the conditioned souls, illusioned by the same energy, are thus unable to know the supreme cause. The most stalwart scientists and philosophers, therefore, cannot be accepted as wonderful. They only appear wonderful because they are instruments in the hands of the illusory energy of the Lord. Under illusion, the general mass of people deny the existence of the Supreme Lord and accept the foolish products of illusory energy as supreme.

One can know the supreme cause, the Personality of Godhead, by the causeless mercy of the Lord, which is bestowed upon the Lord’s pure devotees like Brahmā and those in his disciplic succession. By acts of penance only was Lord Brahmā able to see the Garbhodakaśāyī Viṣṇu, and by realization only could he understand the Lord as He is. Brahmā was extremely satisfied upon observing the magnificent beauty and opulence of the Lord, and he admitted that nothing can be comparable to Him. Only by penance can one appreciate the beauty and opulence of the Lord, and when one is acquainted with that beauty and opulence, he is no longer attracted by any other. This is confirmed in Bhagavad-gītā (2.59): paraṁ dṛṣṭvā nivartate.

Foolish human beings who do not endeavor to investigate the supreme beauty and opulence of the Lord are here condemned by Brahmā. It is imperative that every human being try for such knowledge, and if anyone does not do so, his life is spoiled. Anything that is beautiful and opulent in the material sense is enjoyed by those living entities who are like crows. Crows always engage in picking at rejected garbage, whereas the white ducks do not mix with the crows. Rather, they take pleasure in transparent lakes with lotus flowers, surrounded by beautiful orchards. Both crows and ducks are undoubtedly birds by birth, but they are not of the same feather.