Śatapatha Brāhmaṇa ("of a hundred paths") 3.3.4.8

3.3.4.8

atha yadi dve kṛṣṇājine bhavataḥ | tayoranyataratpratyānahyati pratīnāhabhājanaṃ yadyu ekam bhavati kṛṣṇājinagrīvā evāvakṛtya pratyānahyati pratīnāhabhājanaṃ sūryasya cakṣurārohāgnerakṣṇaḥ kanīnakaṃ yatraitaśebhirīyase bhrājamāno vipaściteti sūryamevaitatpurastātkaroti sūryaḥ purastānnāṣṭrā rakṣāṃsyapaghnannetyathābhayenānāṣṭreṇa parivahanti

If there are two deer-skins, he then puts up the other by way of a flag;--and if there is only one, he cuts off the neck of the deer-skin and puts it up by way of a flag;--with the text (Vâg. S. IV, 32), 'Mount thou the eye of Sûrya, the eye-ball of Agni, where thou fliest along with the dappled (horses), shining through the wise (Sûrya).' He thereby places Sûrya (the sun) in front, thinking, 'May Sûrya, in front, ward off the evil spirits!' They now drive (Soma) about on a safe (cart), unmolested by evil spirits.