यद् आदित्यगतं तेजो जगद् भासयते ऽखिलम् । यच् चन्द्रमसि यच् चाग्नौ तत् तेजो विद्धि मामकम् ॥

yad āditya-gataṃ tejo jagad bhāsayate 'khilam | yac candramasi yac cāgnau tat tejo viddhi māmakam ||

The radiance in the sun illumining the whole world, and in moon and fire — know all that tejas as Mine.

Word by word (3)
yad āditya-gataṃ tejaḥ jagad bhāsayate 'khilam
— that radiance (tejaḥ) residing in the sun (āditya-gatam) which illumines the entire world (jagad akhilam) — the sun's light as cosmic agency
yac candramasi yac cāgnau
— and that which is in the moon (candramasi), and that which is in fire (agnau) — the triad of cosmic luminaries from V6 now claimed as Krishna's tejas
tat tejo viddhi māmakam
— know that tejas (radiance/power) to be Mine (māmakam) — viddhi = imperative 'know this,' the teaching's direct command

The radiance that dwelling in the sun illumines the entire world, that which is in the moon and that which is in fire — know that radiance to be Mine.

A modern analogy

A multiplug socket has many outlets — each device draws current from the same source. The sun, moon, and fire are like different outlets: different in size, temperature, rhythm — but the same current of tejas (luminous power) flows through all of them from one source: Paramātmā.

After V6 negated that the supreme abode is illumined by sun/moon/fire, V12 reveals the other side: those very cosmic lights ARE His tejas. This is not contradiction but completion — V6 says Brahman is not illumined by external light; V12 says that external light IS Brahman's power. The Absolute is not lit by the sun; the sun is lit by the Absolute. The three cosmic luminaries (sun, moon, fire) become a trinity of manifestations of the one Tejas.

This verse begins the 'vibhūti-in-nature' section of Ch.15 (V12-14), parallel to Ch.10's vibhūti catalog but compressed to three cosmic forces. Tejas (radiance) is also a technical term in Vedānta for the luminous faculty of the ātman (cit-śakti = consciousness-as-light). V12-14 bridge the cosmological (sun/moon/fire) and the somatic (plants/digestion/memory) to show the same One permeating all scales.

Public-domain translations (4) compare all →

That light which residing in the sun illumines the whole world, that which is in the moon and in the fire — that light do thou know to be Mine. [1]

The light which residing in the sun illumines the whole world, that which is in the moon and in the fire — know that light to be Mine. [4]

Know that glory to be mine which, dwelling in the sun, lights up the whole world, or in the moon or fire. [9]

That splendor dwelling in the sun which illumines the vast universe, that which is in the moon, and that which is in the fire, know that splendor to be mine. [13]

This verse speaks to

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