nārāyaṇo ’ṅgaṁ nara-bhū-jalāyanāt
tac cāpi satyaṁ na tavaiva māyā
In the Caitanya-caritāmṛta, Ādi-līlā, Chapter Two, text 30, Śrīla Prabhupāda comments on this verse as follows: “This statement which is from Śrīmad-Bhāgavatam (10.14.14) was spoken by Lord Brahmā in his prayers to Lord Kṛṣṇa after the Lord had defeated him by displaying His mystic powers. Brahmā had tried to test Lord Kṛṣṇa to see if He was really the Supreme Personality of Godhead playing as a cowherd boy. Brahmā stole all the other boys and their calves from the pasturing grounds, but when he returned to the pastures he saw that all the boys and calves were still there, for Lord Kṛṣṇa had created them all again. When Brahmā saw this mystic power of Lord Kṛṣṇa’s, he admitted defeat and offered prayers to the Lord, addressing Him as the proprietor and seer of everything in the creation and as the Supersoul who is within each and every living entity and is dear to all. That Lord Kṛṣṇa is Nārāyaṇa, the father of Brahmā, because Lord Kṛṣṇa’s plenary expansion Garbhodakaśāyī Viṣṇu, after placing Himself on the Garbha Ocean, created Brahmā from His own body. Mahā-Viṣṇu in the Causal Ocean and Kṣīrodakaśāyī Viṣṇu, the Supersoul in everyone’s heart, are also transcendental expansions of the Supreme Truth.”
In his commentary on this verse, Śrīla Sanātana Gosvāmī has elaborately explained the expansion of the Viṣṇu, or Nārāyaṇa, incarnations from the original form of Godhead, Lord Śrī Kṛṣṇa. The essence is that although Lord Brahmā was born from Lord Nārāyaṇa, Brahmā now understands that Nārāyaṇa is Himself a mere expansion of the original Personality of Godhead, Lord Śrī Kṛṣṇa.