A beautiful hymn of sun god is found in the fifth chapter of canto three of Vishnu Purana. This is a hymn composed by the sage Yagyavalkya who is one of the greatest worshipers and a direct disciple of Surya Narayana.
Yagyavalkya lost all that he learnt from his guru, because of a disagreement. Yagyavalkya pleased lord Surya with this hymn to gain Vedic wisdom and knowledge. Pleased by this very hymn, the sun god directly taught a new section of veda mantras to sage Yagyavalkya. That section or division of Veda is known as Shukla Yajurveda (the white Yajurveda)