Śatapatha Brāhmaṇa ("of a hundred paths") 4.1.1.9

4.1.1.9

sa gṛhṇāti | vācaspataye pavasveti prāṇo vai vācaspatiḥ prāṇa eṣa grahastasmādāha vācaspataye pavasveti vṛṣṇo aṃśubhyāṃ gabhastipūta iti somāṃśubhyāṃ hyenam pāvayati tasmādāha vṛṣṇo aṃśubhyāmiti gabhastipūta iti pāṇī vai gabhastī pāṇibhyāṃ hyenam pāvayati

He draws (the juice of the first turn of pressing into the cup) with (Vâg. S. VII, 1), 'Grow thou pure for Vâkaspati!' for Vâkaspati (lord of speech) is the out-breathing, and this (Upâmsu) graha is the out-breathing: hence he says, 'Grow thou pure for Vâkaspati!'--'purified by the hands with the sprigs of the bull;' for he purifies it with sprigs of Soma: hence he says, 'with the sprigs of the bull;' and 'purified by the hands (gabhasti-pûta),' he says; for--'gabhasti' being the same as 'pâni' (hand)--he indeed purifies it with his hands.