Shatapatha Brahmana 10.1.1.4

10.1.1.4

atha yo'sya so'graṃ raso'gacat mahattadukthaṃ tamasya taṃ rasamṛkṣāmābhyāmanuyanti tadyattatra yajuḥ purastādetyabhinetaiva tadeti yathādo me'mutraikaṃ tadāhariṣyāmītyevaṃ t

And that vital fluid (essence) of his which flowed upwards (became) the Great Litany: it is in quest of that vital fluid that (the priests) go by means of the Rik and Sâman. And when the Yagus marches in front in this (quest), it is in order to fetch something that that (Veda) goes--even as (one might say), 'That one thing there is mine, I will fetch it,' so does that Yagus go in front (or forward). That (vital fluid) they obtain in the course of a year.