Verse 3.19.1

आदित्यो ब्रह्मेत्यादेशस्तस्योपव्याख्यानमसदेवेदमग्र आसीत् । तत्सदासीत्तत्समभवत्तदाण्डं निरवर्तत तत्संवत्सरस्य मात्रामशयत तन्निरभिद्यत ते आण्डकपाले रजतं च सुवर्णं चाभवताम् ॥ ३.१९.१ ॥

ādityo brahmetyādeśastasyopavyākhyānamasadevedamagra āsīt | tatsadāsīttatsamabhavattadāṇḍaṃ niravartata tatsaṃvatsarasya mātrāmaśayata tannirabhidyata te āṇḍakapāle rajataṃ ca suvarṇaṃ cābhavatām || 3.19.1 ||

1. It has been said, ‘Āditya is Brahman.’ Now this is being explained: This universe was at first non-existent, being without names and forms. [It was not visible, but it existed in a subtle form.] Slowly it manifested itself, as a shoot comes out of a seed. Next it developed into an egg and remained for a whole year like that. It then split in two, one half becoming silver and the other half becoming gold.

Word-for-word explanation:

Ādityaḥ brahma, Āditya [the sun] is Brahman; iti ādeśaḥ, so it is said; tasya upavyākhyānam, [here is] an explanation of that [statement]; idam, this [universe of name and form]; agre asat eva āsīt, was at first unmanifested [i.e., it was without its names and forms]; [lest the word asat give the impression that the universe was like ‘a flower in the sky,’ it is said,] tat, this [universe with its names and forms in a subtle state]; sat āsīt, became manifest; tat, that [subtle universe]; samabhavat, first emerged as a seed; tat āṇḍam niravartata, that developed into an egg; tat, it [i.e., the egg]; saṃvatsarasya mātrām aśayata, lay still for a period of a year; tat, it [the egg]; nirabhidyata, split open; te āṇḍakapāle, those two parts of the egg; rajatam ca suvarṇam ca abhāvatām, turned silver and gold respectively.

Commentary:

Earlier Āditya, the sun, was described as a foot of Brahman. Now this is being explained.

Many people think that the universe was created.

But Vedānta says that something cannot be created out of nothing. The universe has always existed, though sometimes it exists like a seed—invisible and without any names and forms.

But why is the sun being called Brahman? Because without the sun there is only darkness, and we are then not conscious of this universe with its names and forms. The universe is non-existent then. And in the absence of the universe, there is no way of knowing that Brahman exists, for it is this universe with its names and forms that makes us aware that Brahman is behind everything. Brahman manifests itself as this universe.