Chandogya Upanishad 3.3

atha ye 'sya pratyañco raśmayas tā evāsya pratīcyo madhunāḍyaḥ sāmāny eva madhukṛtaḥ sāmaveda eva puṣpam tā amṛtā āpaḥ

The western rays of the sun are the honey-cells behind. The Sâman verses are the bees, the Sâma-veda sacrifice is the flower, the water is the nectar.

tāni vā etāni sāmāny etaṃ sāmavedam abhyatapan tasyābhitaptasya yaśas teja indriyaṃ vīryam annādyaṃ raso 'jāyata

Those very Sâman verses (as bees) brooded over the Sâma-veda sacrifice; and from it, thus brooded on, sprang as its (nectar) essence, fame, glory of countenance, vigour, strength, and health.

tad vyakṣarat tad ādityam abhito 'śrayat tad vā etad yad etad ādityasya kṛṣṇaṃ rūpam

That flowed forth and went towards the sun. And that forms what we call the dark (krishna) light of the sun.