A common understanding is that Nārayāṇa, from whose navel Brahmā was born, spoke the catuḥśloki Bhāgavatam to Brahmā. However, Śrī Jīva Goswami disagrees with this concept, and provides evidence that it was Śrī Kṛṣṇa Himself who revealed the Bhāgavatam to Brahmā.
In Anuccheda 10 of the Bhagavat Sandarbha, he cites Kṛṣṇa’s statement to Uddhava from the Third Canto as direct proof of this point:
purā mayā proktam ajāya nābhye padme niṣaṇṇāya mamādi-sarge
jñānaṁ paraṁ man-mahimāvabhāsaṁ yat sūrayo bhāgavataṁ vadanti
O Uddhava, in the days of yore, at the beginning of creation, while he sat on the lotus growing out of My navel, I spoke to Brahmā about supreme knowledge, which is My transcendental glory, which great sages call Śrīmad Bhāgavatam. (SB 3.4.13)
Śrī Jīva cites two verses from Gopāla-Tāpanī Upaniṣad to prove that Śrī Kṛṣṇa Himself instructed Śrīmad Bhāgavatam to Brahmā:
yo brahmāṇaṁ vidadhāti pūrvaṁ yo vai vedāṁś ca prahiṇoti tasmai taṁ ha devam ātma-buddhi-prakāśaṁ mumukṣur vai śaraṇam ahaṁ prapadye
Anyone desirous of liberation must take shelter of Śrī Kṛṣṇa, who illumines everyone’s mind and intelligence. He created Brahmā at the dawn of creation and instructed him in transcendental knowledge. (GTU 1.22)
Brahmā himself subsequently adds in the same scripture:
tadu hovāca- brahmaṇoSsāvanavarataṁ me dhyātaḥ stutaḥ parārdhānte soSbudhyata gopaveśo me purastādāvirbabhūva
I incessantly mediated upon and eulogized Him; thus at the end of a parārdha [fifty years of Brahmā’s life], He became aware of my prayers and appeared to me in the form of a cowherd boy. (GTU 1.26)
While seated on the lotus, Śrī Brahmā was ordered to perform tapa (penance), which he did for a very long period of time. How did he perform this tapa? The Brahma saṁhitā explains that Brahmā received the Gopāla mantra from Him while seated on the lotus growing out of Śrī Nārayāṇa’s navel [Brahma saṁhitā (5.22-26)], and Brahmā performed penance by means of this mantra to please Gopāla i.e. Kṛṣṇa. This is the reason Śrī Brahmā prays to Kṛṣṇa and not Viṣṇu in the Brahma saṁhitā (govindaṁ ādi purusaṁ tamahaṁ bhajāmi).
In Anuccheda 96, Śrī Jīva again emphasizes this point. He notes that SB 2.9.9 mentions Bhagavān as the speaker of the catuḥśloki to Brahmā. Further, SB 2.9.14 mentions that Brahmā saw the Lord of all Sātvatas (sātvatāṁ patiṁ). This verse, consistent with the Gopāla-Tāpanī Upaniṣad, shows that the Bhagavān of verse 2.9.9 is Śrī Kṛṣṇa and not Nārayāṇa in the form of the puruṣāvatāra Garbhodakaśāyi Viṣṇu. This is because the term sātvatāṁ patiṁ is used exclusively for Kṛṣṇa.
Further, it is not that only the catuḥśloki was revealed by Śrī Kṛṣṇa to Brahmā, but the entire Bhāgavatam was revealed to him. This is seen from SB 12.13.10 which states:
idaṁ bhagavatā pūrvaṁ brahmaṇe nābhi-paṅkaje
sthitāya bhava-bhītāya kāruṇyāt samprakāśitam
Bhagavān first revealed this Śrīmad Bhāgavatam in full, out of His grace to Brahmā, who, frightened by material existence, was situated on the lotus flower that had grown from the Lord’s navel.
To summarize, it was Śrī Kṛṣṇa Himself who spoke the Śrīmad Bhāgavatam in four seed verses (as well as in its complete form) to Śrī Brahmā.