Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.2.5

2.6.2.5

sa jaghanena gārhapatyam | yajñopavītī bhūtvodaṅṅāsīna etāngṛhṇāti sa tata evopotthāyodaṅtiṣṭhannavahantyudīcyau dṛṣadupale upadadhātyuttarārdhe gārhapatyasya kapālānyupadadhāti tadyadeva tāmuttarāṃ diśaṃ sacanta eṣā hyetasya devasya diktasmādetāmuttarāṃ diśaṃ sacante

He takes out (the rice for) those (cakes), while seated behind the Gârhapatya, sacrificially invested and facing the north. From thence he rises and threshes (the rice), while standing with his face towards the north. He places the two mill-stones on (the black antelope skin, so as to incline) towards the north; and puts the potsherds on the north side of the Gârhapatya hearth. As to why they keep the northern quarter,--that indeed is the quarter of that god (Rudra), and hence they keep the northern quarter.