आकाशप्रभवो ब्रह्मा शाश्वतो नित्य अव्ययः।
तस्मान्मरीचिः संजज्ञे मरीचेः कश्यपः सुतः॥
ākāśa-prabhavo brahmā śāśvato nitya avyayaḥ
tasmān marīciḥ saṁjajñe marīceḥ kaśyapaḥ sutaḥ
ākāśa-prabhavaḥ = from the self-effulgent Lord was born; brahmā = Brahmā; śāśvataḥ = who is eternal; nityaḥ = ever-lasting; avyayaḥ = and inexhaustible; tasmāt = from him; marīciḥ = Marīci; saṁjajñe = was born; marīceḥ = Marīci’s; kaśyapaḥ = Kaśyapa; sutaḥ = son was.
“From the self-effulgent Lord was born Brahmā who is eternal, ever-lasting and inexhaustible. From him, Marīci was born. Marīci’s son was Kaśyapa.1
1 Rāmāyaṇa-bhāva-dīpa: āsamantāt kāśamānatvād ākāśo bhagavān.
1 Only He who is transcendental to material names and forms can arrange them; therefore Ākāśa is a name of Brahman. And Lord Caitanya Mahāprabhu has pointed out that Brahman in the context of Vedānta philosophy primarily means Bhagavān. See Caitanya-caritāmṛta Ādi-līlā 7.111 and Madhya-līlā 6.147, 24.73 and 25.33.
2 That is, the post of Brahmā is eternal like a stream of water in a waterfall.
Ākāśa (literally meaning “sky”) refers to the Supreme Brahman, [Lord Nārāyaṇa] here because of this Śruti statement:
ākāśo ha vai nāma-rūpayor nirvahitā. te yad antarā tad brahma.
“Ākāśa arranges for the name and form [of everything material substance]. Brahman is He who is transcendental to those [names and forms].”1 (Chāndogya Upaniṣad 8.14.1)
The statement in Canto 1 (Bāla-kāṇḍa) is made in a similar manner:
avyakta-prabhavo brahmā
“From the unmanifest self-effulgent Lord was born Brahmā.” (Rāmāyaṇa 1.70.19)
Śāśvataḥ (“eternal”) indicates that Brahmā is eternal like a stream [of water in a waterfall].2 Nityaḥ (“ever-lasting”) indicates that Brahmā lives longer than others [and is eternal in a relative sense]. If we take this to mean otherwise, it will contradict the statement that Brahmā was born from the self-effulgent Lord (ākāśa-prabhavaḥ). Avyayaḥ (“inexhaustible”) indicates that one gets liberation from the position of Brahmā.
NOTE. Śrīla Baladeva Vidyābhūṣaṇa in Govinda-bhāṣya (1.3.41) states:
ākāśa-śabdaś ca vyāpakatvād asaṅgatvāc ca paramātmani prayuktaḥ prasiddhaś ca tatraiva.
“The word ākāśa is used to refer to the Supreme Soul because He is all-pervading and because He does not mix [with what He pervades]. Akāśa is also well-known [in the scriptures] to refer to the Supreme Soul.”
Another point to note is that the post of Brahmā is not literally eternal. Prabhupāda explains this thus:
The duration of the material universe is limited. It is manifested in cycles of kalpas. A kalpa is a day of Brahmā, and one day of Brahmā consists of a thousand cycles of four yugas, or ages: Satya, Tretā, Dvāpara and Kali... These four yugas, rotating a thousand times, comprise one day of Brahmā, and the same number comprise one night. Brahmā lives one hundred of such “years” and then dies. These “hundred years” by earth calculations total to 311 trillion and 40 billion earth years. By these calculations the life of Brahmā seems fantastic and interminable, but from the viewpoint of eternity it is as brief as a lightning flash. In the Causal Ocean there are innumerable Brahmās rising and disappearing like bubbles in the Atlantic. Brahmā and his creation are all part of the material universe, and therefore they are in constant flux.
In the material universe not even Brahmā is free from the process of birth, old age, disease and death. (Bhagavad-gītā 8.17 purport)