Śatapatha Brāhmaṇa ("of a hundred paths") 9.4.2.18

9.4.2.18

athārkāśvamedhayoḥ saṃtatīrjuhoti | ayaṃ vā agnirarko 'sāvādityo 'śvamedhastau sṛṣṭau nānaivāstāṃ tau devā etābhirāhutibhiḥ samatanvantsamadudhustathaivaināvayametābhirāhutibhiḥ saṃtanoti saṃdadhāti

He then offers the Arkâsvamedha-santati oblations. The light (arka), doubtless, is this fire (Agni), and the Asvamedha (horse-sacrifice) is yonder sun,--when created, these two were separate: by means of these oblations the gods drew them together and connected them; and in like manner does this (Sacrificer), by means of these oblations, now draw them together and connect them.