CC Adi-lila 01.003 yad advaitam brahmopanisadi... cited
Expressions researched:
"Brahman, the eternal soul, was never born"
|"What the Upanisads describe as the impersonal Brahman is but the effulgence of His body"
|"Ya atmantaryami purusa iti"
|"so 'syamsa-vibhavah"
|"tad apy asya tanu-bha"
|"yad advaitam brahmopanisadi"
Srimad-Bhagavatam
SB Canto 5
What, then, is the ultimate truth? The answer is that nondual knowledge is the ultimate truth. It is devoid of the contamination of material qualities. It gives us liberation. It is the one without a second, all-pervading and beyond imagination. The first realization of that knowledge is Brahman. Then Paramātmā, the Supersoul, is realized by the yogīs who try to see Him without grievance. This is the second stage of realization. Finally, full realization of the same supreme knowledge is realized in the Supreme Person. All learned scholars describe the Supreme Person as Vāsudeva, the cause of Brahman, Paramātmā and others.
In Caitanya-caritāmṛta it is said: yad advaitaṁ brahmopaniṣadi tad apy asya tanu-bhā. The impersonal Brahman effulgence of the Absolute Truth consists of the bodily rays of the Supreme Personality of Godhead. Ya ātmāntaryāmī puruṣa iti so 'syāṁśa-vibhavaḥ. What is known as ātmā and antaryāmī, the Supersoul, is but an expansion of the Supreme Personality of Godhead. Sad-aiśvaryaiḥ pūrṇo ya iha bhagavān sa svayam ayam (CC Adi 1.3). What is described as the Supreme Personality of Godhead, complete with all six opulences, is Vāsudeva, and Śrī Caitanya Mahāprabhu is nondifferent from Him. Great learned scholars and philosophers accept this after many, many births. Vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ (BG 7.19). The wise man can understand that ultimately Vāsudeva, Kṛṣṇa, is the cause of Brahman, and Paramātmā, the Supersoul. Thus Vāsudeva is sarva-kāraṇa-kāraṇam (Bs. 5.1), the cause of all causes. This is confirmed in Śrīmad-Bhāgavatam. The real tattva, Absolute Truth, is Bhagavān, but due to incomplete realization of the Absolute Truth, people sometimes describe the same Viṣṇu as impersonal Brahman or localized Paramātmā.