Śatapatha Brāhmaṇa ("of a hundred paths") 3.9.3.15

3.9.3.15

athāparaṃ caturgṛhītamājyaṃ gṛhītvā | udaṅ prayannāhāpa iṣya hotarityapa ica hotarityevaitadāha tadyadato hotānvāhaitamevaitadyajñasya rasamabhiprastṛṇīte tamārunddha etānu caivaitadanutiṣṭhate nedenānantarā nāṣṭrā rakṣāṃsi hinasanniti

Having then a second time taken ghee by four ladlings, he says, while going forth towards the north, 'Summon the waters!' whereby he means to say, 'Desire the waters, O Hotar!' The reason why the Hotri then recites is this: by that (oblation) he (the Adhvaryu) pours out (the ghee) towards that sap of the sacrifice (in the water), and draws it to him; and he (the Hotri) then stands by those (Ekadhana pitchers) lest the evil spirits should injure them on the way.