Actually this dark universe is illuminated by the sun, but the sun and moon simply reflect the bodily effulgence of the Supreme Lord. In BG (BG 7.8) the Lord says, prabhasmi sasi-suryayoh: "I am the illuminating energy of both the sun and the moon."

Expressions researched:
"Actually this dark universe is illuminated by the sun, but the sun and moon simply reflect the bodily effulgence of the Supreme Lord. In Bhagavad-gītā" |"the Lord says, prabhāsmi śaśi-sūryayoḥ" |"I am the illuminating energy of both the sun and the moon"

Srimad-Bhagavatam

SB Canto 4

The Lord is just like the effulgent sun. Consequently, whenever the Supreme Personality of Godhead is present, there cannot be darkness or ignorance. Actually this dark universe is illuminated by the sun, but the sun and moon simply reflect the bodily effulgence of the Supreme Lord. In Bhagavad-gītā (BG 7.8) the Lord says, prabhāsmi śaśi-sūryayoḥ: "I am the illuminating energy of both the sun and the moon.".

SB 4.30.5, Translation and Purport

The Personality of Godhead, appearing on the shoulder of Garuḍa, seemed like a cloud resting on the summit of the mountain known as Meru. The transcendental body of the Personality of Godhead was covered by attractive yellow garments, and His neck was decorated with the jewel known as Kaustubha-maṇi. The bodily effulgence of the Lord dissipated all the darkness of the universe.

As stated in Caitanya-caritāmṛta (CC Madhya 22.31):

kṛṣṇa—sūrya-sama; māyā haya andhakāra

yāhāṅ kṛṣṇa, tāhāṅ nāhi māyāra adhikāra

The Lord is just like the effulgent sun. Consequently, whenever the Supreme Personality of Godhead is present, there cannot be darkness or ignorance. Actually this dark universe is illuminated by the sun, but the sun and moon simply reflect the bodily effulgence of the Supreme Lord. In Bhagavad-gītā (BG 7.8) the Lord says, prabhāsmi śaśi-sūryayoḥ: "I am the illuminating energy of both the sun and the moon." The conclusion is that the origin of all life is the bodily effulgence of the Supreme Personality of Godhead. This is also confirmed in Brahma-saṁhitā: yasya prabhā prabhavato jagad-aṇḍa-koṭi (BS 5.40). Being illuminated by the bodily effulgence of the Supreme Personality of Godhead, everything is freed from all darkness.