Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.1.11

2.6.1.11

tanmadhye 'gniṃ samādadhāti | purastādvai devāḥ pratyañco manuṣyānabhyupāvṛttāstasmāttebhyaḥ prāṅ tiṣṭhañjuhoti sarvataḥ pitaro 'vāntaradiśo vai pitaraḥ sarvata iva hīmā avāntaradiśastasmānmadhye 'gniṃ samādadhāti

In the centre of this (altar) he lays down the fire. From the east, indeed, the gods came westwards to the men: hence one offers to them while standing with his face towards the east. On all sides are the fathers, for the fathers are the intermediate regions, and the intermediate regions are indeed on all sides: this is why he lays down the fire in the centre.