Śatapatha Brāhmaṇa ("of a hundred paths") 3.8.2.19

3.8.2.19

athottaratastiṣṭhanvapām pratapati | atyeṣyanvā eṣo 'gnim bhavati dakṣiṇataḥ parītya śrapayiṣyaṃstasmā evaitannihnute tatho hainameṣo 'tiyantamagnirna hinasti tasmāduttaratastiṣṭhan vapām pratapati

Thereupon he heats the omentum while standing on the north side; for he is about to pass by the fire and to roast (the omentum) after walking round to the south side. Hereby then he propitiates it, and thus that fire does not injure him while passing by; this is why he heats the omentum while standing on the north side.