Shatapatha Brahmana 4.6.7.21

4.6.7.21

tadvā etadeva puraścaraṇam | ya eṣa tapati sa etasyaivāvṛtā caredgrahaṃ gṛhītvaitasyaivāvṛtamanvāvarteta pratigīryaitasyaivāvṛtamanvāvarteta grahaṃ hutvaitasyaivāvṛtamanvāvarteta sa haiṣa bhartā sa yo haivaṃ vidvānetasyāvṛtā śaknoti carituṃ śaknoti haiva bhāryānbhartum

Now that same puraskarana (going before) is nothing else than yonder burning (sun): one ought to perform in accordance with his (the sun's) course. When he (the Adhvaryu) has drawn a cup of Soma, let him turn round in accordance with his course; when he has responded (to the Hotri's recitation), let him turn round in accordance with his course; when he has offered a graha, let him turn round in accordance with his course: he (the sun), verily, is the supporter; and whosoever, knowing this, is able to perform in accordance with his course, he, forsooth, is able to support his dependants.