Shatapatha Brahmana 6.3.1.29

6.3.1.29

te dakṣiṇatastiṣṭhanti | etadvai devā abibhayuryadvai no yajñaṃ dakṣiṇato rakṣāṃsi nāṣṭrā na hanyuriti ta etaṃ vajramapaśyannamumevādityamasau vā āditya eṣo 'śvasta etena vajreṇa dakṣiṇato rakṣāṃsi nāṣṭrā apahatyābhaye 'nāṣṭrā etaṃ yajñamatanvata tathaivaitadyajamāna etena vajreṇa dakṣiṇato rakṣāṃsi nāṣṭrā apahatyābhaye 'nāṣṭrā etaṃ yajñaṃ tanute

They stand on the south side;--for the gods at that time were afraid, lest the Rakshas, the fiends, should smite their sacrifice from the south. They saw that thunderbolt, yonder sun; for this horse is indeed yonder sun; and by means of that thunderbolt they drove off the Rakshas, the fiends, from the south, and spread this sacrifice in a place free from danger and devilry. And in like manner does the Sacrificer now by this thunderbolt drive off the Rakshas, the fiends, from the south, and spread this sacrifice in a place free from danger and devilry.