Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 11.3.9

11.3.9

uparayanto adhvaram ity upasaṃdadhāti / (soma: prātar anuvāka)

forward up to the sacrifice’, (with this) he continues. ‘Up’ is the symbol of this world, ‘advancing’ is that of yonder (world); ‘up’ is the symbol of Agni, ‘advancing’ is that of yonder sun; so in all the formulae of recourse, in all the services to Agni, to Uṣas, and to the Açvins the first utterance is the symbol of Agni, the second that of yonder sun. There are varied metres and between them pits as it were; these two are the strongest, the uninjured, the untroubled, deities; with these two he commences. With the one hymn should he mount; that is the symbol of mounting without falling into a pit and is heavenly. When there occurs in the one hymn a difference of authorship, then without taking breath should he step over. Breath is immortality; thus by immortality he passes by death; just as one steps over a pit by means of a beam or a roller, so with the Praṇava he steps over; the Praṇava is holy power; verily thus with the holy power he continues the holy power.