Shatapatha Brahmana 1.9.2.2

1.9.2.2

taddhaikeṣāmadhvaryuḥ | pūrveṇāhavanīyam paryeti tadu tathā na kuryādbahirdhā ha yajñātsyādyatteneyāt

Here now the Adhvaryu, according to some, passes the Âhavanîya on the east side. Let him not, however, do this; for were he to walk on that side, he would be outside the sacrifice.