Shatapatha Brahmana 4.1.1.23

4.1.1.23

amuṣminvā etamahauṣīt | ya eṣa tapati sarvaṃ vā eṣa tadenaṃ sarvasyaiva parārdhyaṃ karotyatha yadavarāṃ devatāṃ kuryātparaṃ svāhākāraṃ syādu haivāmuṣmādādityātparaṃ tasmādavaraṃ svāhākāraṃ karoti parāṃ devatām

Now it is in him that burns yonder (the sun) that he has just offered that (libation); and the latter is the All: hence he makes that (sun) the highest of the All. But were he to utter the second (or higher) 'Hail!' with regard to a preceding (or lower) deity, then it would be even higher than yonder sun: therefore he utters the second 'Hail!' with regard to a subsequent deity.