Śatapatha Brāhmaṇa ("of a hundred paths") 3.6.2.20

3.6.2.20

atha yadagnau hoṣyanti | tadvo viṣyatīti sa yadagnau juhvati tadenānavatyatha yadvaḥ somam bibhrata uparyupari cariṣyanti tadvo viṣyatīti sa yadenāntsomam bibhrata uparyupari caranti tadenānavati tasmādadhvaryuḥ samayā dhiṣṇyānnātīyādadhvaryurhi somam bibharti tamete vyāttena pratyāsate sa eteṣāṃ vyāttamāpadyeta tamagnirvābhidahedyo vāyaṃ devaḥ paśūnāmīṣṭe sa vā hainamabhimanyeta tasmādyadyadhvaryoḥ śālāyāmarthaḥ syāduttareṇaivāgnīdhrīyaṃ saṃcaret

'And what they will offer in the fire that will satiate you;' hence that which they offer in the fire satiates them. 'And when they will move about, holding the Soma over each, that will satiate you;' hence when they move about, holding the Soma over each (hearth), that satiates them. Wherefore let not the Adhvaryu pass between the hearths, for the Adhvaryu carries the Soma, and they sit waiting for him (Soma) with open mouths, and he would enter into their open mouths; and either Agni would burn him, or else that god who rules over beasts (Rudra) would seek after him; hence whenever the Adhvaryu should have business in the hall, let him pass north of the Âgnîdhra shed.