Shatapatha Brahmana 13.7.1.5

13.7.1.5

sūryastudukthyastṛtīyamaharbhavati sūryo vai sarve devāḥ sarveṣām devānāmāptyai sauryā grahā bhavanti sauryyaḥ purorucaḥ sarvaṃ sauryamasaditi

The third day is a Sûryastut, Ukthya, for the sake of his gaining and winning all the gods, for Sûrya is all the gods. The cups of Soma pertain to Sûrya, and so do the Puroruk formulas pertain to Sûrya, in order that everything should pertain to Sûrya.